Compact high performance fuel system with accumulator

ABSTRACT

PCT No. PCT/US94/05108 Sec. 371 Date Jun. 16, 1995 Sec. 102(e) Date Jun. 16, 1995 PCT Filed May 6, 1994 PCT Pub. No. WO94/27041 PCT Pub. Date Nov. 24, 1994A unitized fuel supply assembly is disclosed including an in-line reciprocating cam driven pump (14) for supplying fuel to an accumulator (12) from which fuel is directed to a plurality of engine cylinders by means of a distributor (16) mounted on the unitized assembly. Dual pump control valves (20) provide fail safe electronic control over the effective pump displacement. One or more injection control valves mounted on the distributor are provided to control injection timing and quantity. The accumulator (12) contains a labyrinth of interconnected chambers (36) which are shaped and positioned to produce a minimum overall package size while providing for easy manufacture.

This application is a continuation-in-part application of the followingU.S. patent applications: Ser. No. 057,489 filed May 6, 1993, nowabandoned; and Ser. No. 117,697, filed Sep. 8, 1993, now U.S. Pat. No.5,353,766.

TECHNICAL FIELD

This invention relates to a fuel system for an internal combustionengine and more particularly to a fuel system for a multi-cylindercompression ignition engine including a high pressure fuel pump and fuelaccumulator.

BACKGROUND

For well over 75 years the internal combustion engine has been mankind'sprimary source of motive power. It would be difficult to overstate itsimportance or the engineering effort expended in seeking its perfection.So mature and well understood is the art of internal combustion enginedesign that most so called "new" engine designs are merely designs madeup of choices among a variety of known alternatives. For example, animproved output torque curve can easily be achieved by sacrificingengine fuel economy. Emissions abatement or improved reliability canalso be achieved with an increase in cost. Still other objectives can beachieved such as increased power and reduced size and/or weight butnormally at a sacrifice of both fuel efficiency and low cost.

An engine's fuel system is the component which often has the greatestimpact on performance and cost. Accordingly, fuel systems for internalcombustion engines have received a significant portion of the totalengineering effort expended to date on the development of the internalcombustion engine. For this reason, today's engine designer has anextraordinary array of choices and possible permutations of known fuelsystem concepts. Design effort typically involves extremely complex andsubtle compromises among cost, size, reliability, performance, ease ofmanufacture and backward compatibility with existing engine designs.

The challenge to contemporary designers has been significantly increasedby the need to respond to governmentally mandated emissions abatementstandards while maintaining or improving fuel efficiency. In view of themature nature of fuel system designs, it is extremely difficult toextract both improved engine performance and emissions abatement fromfurther innovations in the fuel system art. Yet the need for suchinnovations has never been greater in view of the series of escalatingemissions standards mandated for the future by the United Statesgovernment. Meeting these standards, especially those for ignitioncompression engines, will require substantial innovations in fuelsystems unless engine manufacturers are prepared to adopt significantlymore costly fuel systems and/or engine redesigns. For example, CumminsEngine Company, Inc., assignee of the subject application, presentlymanufactures a pair of mid-range compression ignition engines identifiedas the B series and C series (5.9 and 8.3 liters displacementrespectively). These engines employ a state of the art pump-line-nozzle(PLN) type of fuel system provided to Cummins by another manufacturer.However, this type of fuel system will not permit the B and C seriesengines to meet the future emissions abatement standards imposed by theUnited States government.

Among the universe of known fuel systems are several concepts whichwould appear initially to provide a possible solution to the requirementfor improved emissions abatement and satisfactory engine performance.However, for the various reasons outlined below these systems areinadequate.

One possibility pioneered by the assignee of this invention is disclosedin U.S. Pat. No. 5,042,445 to Peters et al. This patent discloses a camdriven unit injector designed to provide very high injection pressures(30,000 psi or higher) even at low engine speeds. Such high injectionpressures promote better fuel vaporization during injection therebyhelping to assure complete combustion and thus reduced emissions in theengine exhaust. Implementation of this concept requires a unit injector(defined as a single unit device combining a fuel injection nozzle andhigh pressure pump) adjacent each engine cylinder wherein the injectoris designed to achieve the desired high injection pressure at low enginespeeds. The Peters et al injector is equipped with a hydraulic variablelength chamber for controlling the timing of each injection event inresponse to engine conditions. Excessive pressures are avoided in thistype of injector at elevated engine speeds by the provision of apressure relief valve for dumping timing fluid during the injectionstroke of the unit fuel injector.

Other types of unit fuel injectors are known which are capable ofadequate high pressure injection and sufficiently precise injection toachieve some of the performance objectives discussed above. One exampleis disclosed in SAE Paper No. 911819 relating to a PDE unit injectordeveloped by Bosch. Still another is disclosed in U.S. Pat. No.4,531,672 to Smith assigned to the assignee of this application.

While the unit injectors described above are capable in many ways ofachieving the desired performance objectives, major cost penalties areassociated with adoption of such injectors on pre-existing enginedesigns. In particular, retro-fitting an existing engine such as theCummins B series or C series engine with one of the above described unitinjector designs would require a major overhaul of the engine. Inparticular, when these types of injectors were considered for the B andC engines, it became clear that a redesigned block, head, front end andall associated parts would be required. In short, a substantially newengine would be required with an attendant retooling investment inexcess of several hundred million dollars.

Another approach for achieving the desired high pressure injection andvariable timing required to meet the escalating emissions limitationstandards is disclosed in a fuel system offered by Bosch under thedesignation PLD. This design approach is characterized by the provisionof a separate high pressure pump unit associated with each enginecylinder and connected through a short line to a nozzle arranged toinject fuel into the associated cylinder. Each pump unit is individuallypackaged separate from the associated nozzle and from all other pumpunits associated with the engine. The pump units are mounted on theengine for actuation by the engine cam shaft as close as possible to theassociated engine cylinder. Although this approach has fuel system costand performance advantages resulting from the use of existing enginecomponents and minimal impact on the head design, major changes would berequired in the engine block. More particularly, the block would need tobe entirely redesigned to accommodate the attachment of the individualpump units along the engine cam shaft. Implementation of this approachon the B and C engines would require an investment estimated to be inthe neighborhood of several tens of millions of dollars.

One high performance approach requiring less engine redesign isdisclosed in U.S. Pat. No. 5.096,121 to Grinsteiner. This style of unitinjector includes a fluid pressure intensifying piston which has theeffect of multiplying the pressure of a motive fluid, such aspressurized lubrication oil, by the ratio of the effective crosssectional areas of the intensification piston contacted on its larger,low pressure side by the motive fluid and on the smaller, high pressureside by the engine fuel. Such a design has the potential for achievingmany of the desired performance objectives but some significant redesignof the base engine is still required. For example, the system requiresan entirely new cylinder head to accommodate not only the injector butalso the oil accumulator that provides the intensification. A separatelubrication circuit or a totally redesigned lubrication circuit must beprovided to supply the motive fluid through a control valve to theintensification piston. Such an system would require a separate suctiontube, oil pump, and filtration system.

The cost for base engine redesign required by a fluid intensificationunit injector is likely to be considerably less than the engine redesigncosts associated with adoption of any of the other unit injector andunit pump concepts described above. Nevertheless, Cummins estimates thatadoption of fluid intensifiers on the B and C series engines would stillrequire an investment in the range of multiple tens of millions ofdollars. In addition to the costs associated with redesign of theengine, the fuel system itself including the hydraulic unit injectors,redesigned lubrication circuit, filters and associated equipment wouldlikely be far more expensive than many other known types of fuelsystems. U.S. Pat. Reissue No. 33,270 to Beck et al. discloses anothertype of hydraulic intensifier unit injector which would appear to supplythe same benefits but suffer the same drawbacks discussed above.

Yet another approach to meeting the goal of increased fuel systemperformance would be to provide an accumulator for storing the output ofa high pressure pump and to provide a plurality of injection nozzlesconnected with the accumulator and associated with the engine cylinderswherein each nozzle includes a separate integrated solenoid valve tocontrol the timing and quantity of fuel flow from the accumulator intoeach cylinder. Examples of this type of system are disclosed in U. S.Pat. No. 5,094,216 to Miyaki et al. and SAE article no. 910252 entitledDevelopment of New Electronically Controlled Fuel Injection SystemECD-U2for Diesel Engines by Miyaki et al. This system allows theaccumulator pressure (and thus the injection pressure) to be regulatedas necessary independent of engine speed. However, solenoids capable ofhandling the very high pressure and the necessary fast response timesare relatively bulky and costly. Such solenoids will require severe headredesign on the C series and some modification on the B-series engines.Also, mounting of the high pressure accumulator on an internalcombustion engine is not necessarily simple nor does it yield anuncluttered engine package or appearance. While the total engineredesign costs would be less than the engine redesign costs associatedwith adoption of the fuel systems noted above, the costs associated withthe fuel system components themselves, including the high pressure pumpand solenoid controlled injection nozzles, could be prohibitively high.

The above described approaches could potentially achieve many of thedesired performance objectives but a major cost penalty is associatedwith each design either in the form of a costly engine redesign or addedfuel system costs or both. Other less costly fuel system concepts areknown but these concepts fail to provide the full complement ofperformance objectives desired.

One approach which would require virtually no engine redesign involvesthe provision of a high pressure "in-line" pump such as offered by Boschunder the designation P7100. In this type of system injection nozzleslocated at each engine cylinder are connected through separate lines tocorresponding pumping chambers contained within the housing of a singleunitized high pressure pump. The chambers are aligned along the axis ofa pump drive shaft and contain corresponding plungers mounted to bereciprocated by the pump drive shaft in synchronism with the enginecrankshaft. With appropriate design and controls, in-line systems ofthis type can achieve the necessary pressures and injection accuracyunder some engine conditions but can not be relied upon to provide thedesired performance objectives over the long term especially at lowengine speeds. Further, in-line fuel pumps which are capable ofapproaching some of the more important pressure and control objectivesare enormously more expensive than the present pump line nozzle systemused on the Cummins B and C series engines.

Another fuel system which would necessitate little redesign of the basicengine involves the use of a rotary pump design. This type of pump ischaracterized by a pump housing containing a plurality of radiallyoriented pump chambers within which are mounted plungers adapted to bereciprocated by a cam surface located at the center of the pump housing.U.S. Pat. Nos. 4,498,442 and 4,798,189 disclose examples of this type ofpump. Although engine impact is low and cost is relatively low, rotarypumps lack performance capability at higher engine ratings. Inparticular, rotary pumps are not capable of providing the desired volumeor the desired high pressure over the full operating range of a typicalengine.

Still another fuel system concept is disclosed in Japanese Pat.Application Document 57-68532 to Nakao and assigned to Komatsu. Thisreference discloses an electronically controlled high pressure pump andan accumulator for receiving the pump output for supply of a pluralityof injection nozzles through a distributor type valve and correspondingfuel supply lines. The timing and quantity of injection is controlled bymeans of rotary valve elements combined with the distributor valve. Thepressure within the accumulator is regulated by a feedback signalresponsive to the accumulator pressure to control the effectivedisplacement of the high pressure pump. While this design has featuresof interest, it fails to disclose how to achieve the necessary operatingpressures in a unitized assembly of sufficiently compact size to allowthe resulting system to be mounted in a practical manner on an internalcombustion engine. No provision is made for operating the system in afail safe manner in case one or more of the electronic controlmechanisms should fail during operation. Furthermore, the designprovides for an entirely separate pump assembly and accumulatorcomponents connected by a plurality of separate fluid lines which wouldmultiply the sites of potential leaks.

The Komatsu reference also fails to teach how to manufacture in apractical manner an accumulator so that the very high pressures, i.e.5,000 to 30,000 psi or higher, could be stored within a compact packagehaving adequate fuel storage capacity with freedom from potentialleakage or dangerous failure. The Komatsu reference further fails tosuggest how to design and assemble the system to achieve an acceptablylow manufacturing cost. The disclosed distributor valve would also notbe suitable for handling the very high pressures required for the systemwithout simultaneously giving rise to a high probability of fuel leakagethat would cause excessive parasitic loses, that is an excessive amountof mechanical energy would be required to drive the fuel system pumpthat would otherwise be available as useful output from the engine.

Still other references have disclosed the concept of providing anaccumulator in a fuel system wherein fuel from the accumulator canalternatively be controlled for injection into the respective enginecylinders either by a distributor valve or a plurality of solenoidsassociated with each of the individual injector nozzles. German PrintedPat. Application No. DE 3618447 Al assigned to Bosch discloses anexample of this type of system. The highly schematic disclosure of thisteaching, however, causes this reference to fail to teach how to solvethe problems referred to with respect to the Komatsu reference.

Attempts have been made to design a high pressure common rail oraccumulator for storing the output of a high pressure pump for deliveryto injection nozzles. For example, U.S. Pat. No. 5,109,822 to Martindiscloses a high pressure common rail fuel injection system including acommon rail formed from a one-piece metal housing having a series ofelongated bores formed therein for temporarily storing the high pressurefuel delivered by a high pressure pump. However, Martin fails to teachhow to determine the optimum arrangement of elongated chambers or boresfor producing a compact common rail with minimum outer dimensions whichfit within existing available mounting envelopes required by existingengines while ensuring that the common rail housing walls aresufficiently strong to withstand the forces generated by the very highoperating pressure of the fuel in the chambers. In addition, Martin doesnot disclose how to ascertain the minimum required fuel storage volumefor the common rail which is a primary factor in designing a compactcommon rail. Also, the common rail disclosed in Martin is not integratedwith the high pressure pump unit and/or other components, such as a fuelpump control valve, to form a compact fuel delivery assembly which iscapable of efficiently controlling the pressure in the common rail. U.S.Pat. No. 2,446,497 to Thomas discloses a high pressure pump, a commonhigh pressure chamber or accumulator, a distributor and fuel injectioncontrol governors mounted adjacent one another to form a combined fuelinjection assembly. However, Thomas fails to disclose a fuel assemblywhich is highly compact and integrated, and also capable of efficientlyand effectively controlling both the pressure in the accumulator andinjection timing and quantity.

Attempts have also been made to design high pressure, high speedsolenoid operated valves for use in fuel systems for compressionignition internal combustion engines. For example, U. S. Pat. No.3,680,782 to Monpetit et al discloses an electronically controlled fuelinjector employing a force balanced three-way valve having a nearlyforce balanced "pin-in-sleeve" valve member design. In valves of thistype, the movable valve member is movable between first and secondpositions to alternatively connect an output valve passage to one of twoalternative valve passages, typically a high pressure source and adrain. The movable valve member contains a cavity opening at one end totelescopingly receive a floating pin. A first valve seat is formedbetween the sleeve and the surrounding valve housing and a second valveseat is formed between the sleeve and pin. The valve element is movablebetween a first position in which the injector nozzle is connected witha source of fuel under high injection pressure and a second position inwhich the valve element isolates the source of fuel from the injectionorifices of the nozzle and connects the passage leading to the injectionorifices to a drain to insure near instantaneous termination of eachinjection event.

Other examples of three-way high speed, high pressure fuel system valvesare disclosed in U.S. Pat. No. 5,038,826 to Kabai et al (Nippondenso).While capable of handling high pressure and operating at high speed, the"pin-in-sleeve" arrangements of the Monpetit et al. and Nippondensoreferences do not permit the effective valve seats of each discloseddesign to be substantially unequal in size while maintaining the valvemember substantially force balanced.

Another important feature of an effective fuel delivery system is theability to regulate the injection pressure as necessary independent ofengine speed. U.S. Pat. No. 5,094,216 to Miyaki et al. and U.S. Pat. No.4,502,445 to Roca-Nierga et al. both disclose a plural chamber "in-line"fuel pump assembly having an output control device which varies theeffective displacement of one or more pump plungers by providing aseparate pump control valve for each pump chamber which operates to varythe beginning of injection with a constant end of injection occurringwhen the pumping plunger reaches its top dead center position.Specifically, fuel is supplied to the pumping chamber during theretraction stroke and then pumped out of the pumping chamber during theadvancing or pumping stroke until the control valve is closed blockingthe discharge of fuel from the chamber thereby commencing injection ordelivery. The delivery or discharge from the pumping chamber is finishedonly at the end of the pumping stroke of the plunger.

Yet another important feature of an effective fuel delivery systemcapable of meeting the ever increasing requirements of emissionsabatement is the ability to control the rate of fuel delivery duringeach injection event. It has been shown that the level of emissionsgenerated by the diesel fuel combustion process can be reduced bydecreasing the volume of fuel injected during the initial stage of theinjection event. One method of reducing the initial volume of fuelinjected during each injection event is to reduce the pressure of thefuel delivered to the nozzle assemblies during the initial stage ofinjection. Various devices have been developed to control or shape therate of fuel delivery during the initial phase of fuel injection so asto reduce the fuel pressure delivered to the nozzle assemblies. Forexample, U.S. Pat. Nos. 3,718,283, 3,747,857, 4,811,715 and 5,029,568disclose devices associated with each injector nozzle assembly forcreating an initial period of restricted fuel flow and a subsequentperiod of substantially unrestricted fuel flow through the nozzleorifice into the combustion chamber. However, these rate control devicesrequire modifications to each of the fuel injector assemblies in amulti-injector system thus adding costs and complexity to the injectionsystem. U.S. Pat. No. 4,469,068 to Kuroyanagi et al. discloses adistributor-type fuel injection apparatus including an variable volumeaccumulator to vary the rate of fuel injection to achieve effectivecombustion. However, this device uses a complex accumulator controlsystem to vary the rate of injection which is specifically designed tobe used with a distributor having a reciprocating plunger.

Distributor-type fuel injection systems are also subject to anotherundesirable phenomena known as secondary injection. When the nozzleelement of the nozzle assembly closes at the end of each injectionevent, reverse pressure waves or pulses are generated which travel backupstream in the fuel delivery lines to the distributor or deliveryvalves. Under certain operating conditions, these pressure waves may bereflected back toward the nozzle assembly by the distributor or deliveryvalve creating a secondary nozzle operating pulse of sufficientmagnitude to cause the nozzle valve to lift from its seat causing anundesired secondary injection. U.S. Pat. No. 4,246,876 to Bouwkamp etal. discloses a conventional "snubber valve" used to dampen or diffusethe pressure wave energy traveling from the nozzle valve therebypreventing secondary injection by minimizing the intensity of anyresultant reflected pressure wave. However, this design requires aseparate snubber valve to be used in each fuel injection line thusadding cost to the system. U.S. Pat. Nos. 4,336,781, 4,624,231 and5,012,785 all disclose rotary distributor fuel delivery systems using asingle snubber-type valve positioned in the rotary shaft of thedistributor to dampen pressure waves in each injection line.

In order to achieve accurate and predictable injection quantities offuel during each injection event, it is important to ensure that thefuel transfer circuit connecting the fuel supply to the nozzleassemblies is continuously full of fuel. It has been found that vaporpockets or voids (called cavitation) in the transfer circuit result ininsufficient injection pressure and variations in both fuel quantity andtiming of injection. Vapor pockets or voids are especially prone to beformed in high pressure lines of fuel systems where such lines areconnected to a low pressure drain. When the fuel transfer circuit, andthus an injection line, is connected to drain at the end of theinjection event, fuel at one end of the injection line exits out of thenozzle while fuel at the other end of the circuit exits to drain thusrapidly drawing fuel away from, and reducing the pressure in,intermediate portions of the circuit and injection line. This effect canresult in the formation of a vapor pocket or void in the fuel transfercircuit and injection line between the drain and nozzle. Snubber valves,mentioned hereinabove with respect to the prevention of secondaryinjections, are also used to prevent excessive cavitation by allowingsubstantially full flow through an injection line to an injector whilerestricting the return flow of fuel from the injector therebymaintaining fuel in the fuel delivery lines. For example, Japanese Pat.Publication 05-180117 discloses a damping valve positioned downstream ofa delivery valve for preventing cavitation erosion. The damping valveincludes a spring-biased valve element having an orifice and a pressureregulation valve positioned in a bypass channel. This device appears toregulate the fuel pressure in the fuel injection line between thedamping valve and a fuel injection valve to below a preset maximum.

In short, the prior art does not provide a practical, low cost fuelsystem which satisfies the conflicting demands of emissions control andimproved engine performance especially in situations where it is desiredto retrofit a pre-existing engine design. Moreover, there does not existthose fuel system components (such as accumulators, solenoid valves, andinjection control valves) having all the characteristics necessary forproviding fuel under extremely high pressure in precise quantities atprecise times as determined by controls that are responsive to a widerange of engine conditions.

SUMMARY OF THE INVENTION

It is a general object of the subject invention to overcome thedeficiencies of the prior art and in particular to provide a practical,low cost fuel system which satisfies the conflicting demands ofemissions control and improved engine performance. In particular, thesubject invention provides superior emissions control and improvedengine performance while requiring minimal modification of pre-existingengines designs.

It is another object of the subject invention to provide anelectronically controllable, high pressure fuel pump assembly includinga pump, accumulator and distributor combined with an electricallyoperated pump control valve and a injection control valve mounted on theunitized assembly. By this arrangement, a highly integrated fuel systemmay be designed, built and installed either for an original orpre-existing engine design.

Still another object of the subject invention is to provide a fuelsystem for an internal combustion engine of the compression ignitiontype which is capable of achieving very high injection pressures, i.e.,5000-30,000 psi and preferably in the range of 16,000-22,000 psi withprecise control over quantity and timing in response to varying engineconditions.

Still another object of the subject invention is to provide a highperformance, high pressure fuel system designed for retrofitting onexisting engine designs of the compression ignition type withoutrequiring substantial and costly engine redesign. In particular, thesubject invention provides a fuel system having the abovecharacteristics while also improving engine efficiency by minimizing theparasitic losses even though fuel pressure is raised to a very highlevel.

It is a further object of the subject invention to provide a highlyintegrated fuel system characterized by high pressure injection, minimalimpact on pre-existing engine designs, precise control over injectionquantity and timing, redundant fail safe electronic components, andimproved engine efficiency at overall reduced costs with respect tocompeting prior art systems.

It is yet another object of the subject invention to provide a fuel pumpassembly characterized by the combination of a pump, distributor andaccumulator wherein the accumulator includes a housing containing afluidically interconnected labyrinth of accumulator chambers sized andrelatively positioned to create an ideal integrated package.

Another object of the subject invention is to provide an improved fuelsystem capable of providing sufficiently high operating injectionpressures to achieve significant emissions abatement wherein the systemincludes a unitized assembly of sufficiently compact size to allow theresulting system to be mounted in a practical manner on existinginternal combustion engines without creating a cluttered, unsightlyengine appearance.

Another object of the subject invention is to provide a fuel systemhaving the above characteristics wherein the number of fuel leakagesites is minimized by the reduction of system components and theprovision of fail safe redundant low pressure fuel drains throughout thesystem to catch and return to the fuel system any fuel which may leakthrough primary seal areas.

A still further object of the subject invention is to provide a fuelpump assembly including a pump housing having a pump cavity oriented ina radial direction, and an accumulator mounted on the pump housinghaving an overhang in either the lateral and/or axial direction and apump control valve mounted on the overhang portion of the accumulatorhousing adjacent the pump housing to create a highly compact, integratedfuel pump assembly.

Yet another object of the subject invention is to provide a fuel pumpassembly including a fuel pump supplying high pressure fuel, i.e., 5,000to 30,000 psi and preferably 16,000 to 22,000 psi with a pump cavityopening into a head engaging surface and an accumulator adapted toreceive the output of the pump and store temporarily the fuel at thehigh operating pressure for subsequent injection into the internalcombustion engine wherein the accumulator is mounted in contact with ahead engaging surface of the fuel pump to form an end wall for the pumpcavity.

Still another object of the subject invention is to provide a fuel pumpassembly including a pump housing containing a radially oriented pumpcavity, and an accumulator housing mounted adjacent one end of the pumphousing having at least one chamber and a lateral extent to cause theaccumulator to form an overhang in either the lateral or axial directionperpendicular to the radially oriented cavity in further combinationwith an injection valve for directing high pressure fuel in timedsynchronism with engine operation to various engine cylinders whereinthe distributor is cantilever mounted on the pump housing in spacedapart relationship with the accumulator overhang.

Still another object of the subject invention is to provide a fuel pumpassembly including a pump housing having a cavity oriented in a radialdirection, and an accumulator housing mounted on the pump housing at oneend of the pump housing to form a cantilevered lateral overhang suchthat the overhang forms an offset transverse profile for the fuel pumpassembly to complement the irregular transverse profile of the internalcombustion engine on which the fuel assembly is designed to be mounted.

Still another object of the subject invention is to provide a fuel pumpassembly including a pump housing containing a pump cavity, a driveshaft adapted to be mounted in the pump housing, a pump head mounted onthe housing opposite the drive shaft and a pump unit retained in thepump head by means of a retainer which causes the pump unit to extendinto the pump cavity of the pump housing in spaced apart non-contactingrelationship with the pump housing, whereby the pump unit may berelatively easily removed and replaced to provide inexpensive overhaulof the pump assembly and/or the ability to switch pump units to adjustthe effective displacement of the fuel pump assembly.

It is yet another object of the subject invention to provide anaccumulator for a fuel pump system in which the accumulator is formed bya housing containing a fluidically interconnected labyrinth of chamberswherein the housing is formed of an integral one piece block.

It is a more specific object of the subject invention to provide aunitized fuel pump assembly for periodic injection of fuel throughplural fuel injection lines into corresponding engine cylinders of aplural cylinder internal combustion engine. The assembly includes a pumpfor pressurizing fuel, an accumulator for accumulating and temporarilystoring fuel under pressure received from the pump. The accumulator ismounted on the pump housing opposite the drive shaft of the pump with aplurality of pump cavities positioned intermediate the drive shaft andaccumulator. The fuel pump assembly further includes a fuel distributorfor providing periodic fluidic communication between the accumulator andeach of the engine cylinders through the corresponding fuel injectionlines. The fuel distributor is mounted on the pump housing adjacent oneend of the drive shaft and includes a injection control valve forcontrolling the timing and quantity of fuel injected into each cylinderin response to engine operating conditions. The control valve includes asolenoid operator mounted on the distributor housing and is orientedgenerally in the same radial direction as the pump cavities relative tothe rotation axis of the drive shaft. By this arrangement, an extremelycompact, highly integrated fuel pump assembly is formed which maximizeslow cost, reduced size, and high performance in a fuel system adapted tobe provided on new or existing engine designs.

Still another object of the subject invention is to provide a unitized,single piece fuel pump housing containing plural outwardly opening pumpcavities, a radially enclosed drive shaft, a pump head engaging surfaceand plural tappet guiding surfaces within corresponding pump cavitieswherein the tappet guiding surfaces, head engaging surface and driveshaft mounting surfaces are the only surfaces requiring close machiningto create adequate alignment between the drive shaft and the cooperatingfuel pumping elements of the pump.

It is yet another object of the subject invention to provide a fuel pumpincluding an accumulator, a distributor feeding fuel to plural enginecylinders, and a pair of associated pump control valves for controllingdisplacement of the pump elements to cause the pump elements to sharethe load necessary to maintain desired fuel pressure. A first injectioncontrol valve is provided to control a pre-injection portion of theinjection for each cylinder and a second injection control valveassociated with the first injection control valve is provided to controla main injection portion of the injection for each cylinder. Anelectronic control means is further provided for causing an associatedvalve to take over if one of the control valves (pump or injection)should become disabled.

It is yet another object of the subject invention to provide a pumpassembly including a pump housing containing a pump plungerreciprocating along a first pump axis, a drive shaft rotating about adrive axis perpendicular to the pump axis and an accumulator having atleast one elongated chamber mounted on the pump housing with the centralaxis of the chamber being parallel with the drive shaft axis of thepump. By this arrangement, an ideally compact arrangement of an unitizedaccumulator type pump assembly may be formed within a minimum packagesize while providing an adequate total volume of high pressure fuel.

Another object of the subject invention is to provide a fuel pumpassembly providing one or more of the above objects and furtherproviding a pump housing having plural pump chambers and plural solenoidoperated pump control valves corresponding in number to the pumpchambers for controlling the effective displacement of associated pumpplungers operating within each pump chamber. By this arrangement, apressure signal representative of the pressure of the fuel in the fuelpump accumulator may be used to control the solenoid operated pumpcontrol valves to adjust thereby the effective displacement of theplungers to cause the pressure of fuel in the accumulator to equal apredetermined pressure level.

It is an object of the subject invention to provide dual injectioncontrol valves for use on a distributor in combination with a fuel pumpsystem designed in accordance with the subject invention wherein anelectronic control is provided to allow at least "limp-home" operationof the engine should one of the injection control valves becomedisabled.

Another object of the subject invention is to provide a distributorincluding an injection control valve for controlling the timing andquantity of fuel injected into each cylinder in response to engineoperating conditions wherein the injection control valve includes athree-way valve operable when energized to connect an axial supplypassage in the distributor rotor with a high pressure fuel accumulatorand operable when de-energized to connect the axial supply passage inthe distributor rotor with a low pressure drain.

Yet another object of the subject invention is to provide a distributorhousing arranged to control the flow of fuel through a fuel feed linefrom an accumulator to each one of a plurality of engine cylinders bymeans of a pair of three-way valves located in a supply plane transverseto the rotational axis of a distributor rotor wherein the three-wayvalves are received within first and second valve cavities located onopposite sides of the distributor rotor and are interconnected by supplyand drain passages. The valve cavities are further connected by a rotorfeed bore for supplying high pressure fuel to the distributor rotor. Theinjection valve is further characterized by a two way check valvelocated within the rotor feed bore to prevent fuel supplied from onevalve cavity from flowing into the other valve cavity.

Yet another object of the subject invention is to provide a fuel pumpassembly including cam driven reciprocating plungers driven bycorresponding cams having at least one lobe for causing an associatedpump plunger to undergo an advancing stroke and a return stroke for eachrevolution of the camshaft wherein the total number of lobes areselected to produce a pumping event for each injection event.

Yet another object of the subject invention is to provide a replaceablepump unit for each of the respective pump cavities in the pump housingdesigned in accordance with the subject invention wherein each pump unitincludes a barrel containing a pump chamber and a barrel retainer formounting the pump unit in a recess of the fuel pump assemblyaccumulator. A check valve is provided to allow one way fuel flow fromthe pump chamber into the accumulator. The check valve is associatedwith a disk positioned at one end of the barrel to form an end wall ofthe pump chamber. The disk contains both inlet and outlet passages andthe retainer is formed to provide a clearance with the barrel and diskto provide a pathway for return of fuel leakage to a fuel supply passagecontained in the accumulator.

It is yet another object of the subject invention to provide a highpressure fuel pump assembly including an accumulator for storing fuelprior to distribution to corresponding cylinders in an internalcombustion engine by means of an injection valve wherein the accumulatorhas a total volume sufficient to prevent fuel pressure from droppingmore than approximately 5-15 percent, and preferably 5-10 percent,during any injection event depending upon such factors as thecompressibility of the fuel, the operating pressure of the fuel, themaximum potential required injection volumes, timing range and injectionduration selected for the engine, the maximum effective displacement ofeach pump unit, the fuel leakage of the system, the compression of thefuel in the fuel lines, and the fuel lost to drain during valve membertravel between fully opened and fully closed positions.

It is yet another object of the subject invention to provide anaccumulator for the fuel system designed in accordance with the subjectinvention wherein the accumulator contains a labyrinth ofinterconnecting chambers wherein the chambers are elongated andcylindrical in shape and are positioned in generally parallelrelationship. The accumulator chambers are ideally positioned tointersect a vertical plane through the accumulator housing in a twodimensional array.

Still yet another object of the subject invention is to provide arotatable pump and a distributor integrated with a single drive shaftassembly to form a compact fuel system assembly capable of accuratelyand reliably delivering precise quantities of fuel to an engine whileminimizing the size and weight of the assembly.

Yet another object of the present invention is to provide a highpressure fuel pump assembly including a fuel distributor having axiallyslidable spool valves in combination with a separate injection controlvalve.

A further object of the present invention is to provide a fuel pumpassembly including an ultra-compact pump head and integral pump chamberwhich minimizes high pressure fuel leakage while reducing the size andweight of the assembly.

Another object of the present invention is to provide a variety of pumphead/accumulator designs for accommodating pump control valves and checkvalves in various orientations to minimize unwanted fuel leakage,trapped volume and the size and weight of the assembly.

A still further object of the present invention is to provide a fuelpump assembly having a transversely oriented pump control valve forreducing to an absolute minimum the trapped volume within the pumphead/accumulator.

A further object of the present invention is to provide a fuel pumpassembly having a pump unit and a transverse pump control valve mountedin the barrel of the pump unit.

Yet another object of the present invention is to provide variousaccumulator designs for simplifying the formation and manufacture of theaccumulator while minimizing the possibility of undesired fuel leakagefrom the accumulator chambers.

It is yet another object of the present invention to provide a highpressure fuel system having a separately mounted accumulator forpermitting placement of the accumulator in possibly moreappropriate/advantageous locations around the engine while also reducingthe size of the pump head thereby creating a more compact assembly whichmay more appropriately fit with the packaging constraints of certainengines or vehicle designs.

It is yet another object of the present invention to provide variousedge filter mounting concepts for positioning an edge filter within thedisclosed system for preventing damage to the system's components bysmall, foreign particles.

Yet another object of the present invention is to provide rate-shapingcapability for controlling the amount of fuel injected during theinitial portion of the injection event by controlling the increase inpressure at the nozzle assembly.

Another object of the present invention is to provide various cavitationcontrol devices to minimize the formation of vapor pockets or voidswithin the fuel passages of fuel systems thereby minimizingcavitation-induced anomalies in fuel injection metering and timing.

Still another object of the present invention is to provide a novel highpressure fuel system including rate shaping and cavitation controldevices capable of maximizing the rate shaping capability of the systemwhile minimizing cavitation.

A further object of the present invention is to provide a single devicefor permitting rate shaping while also effectively minimizing cavitationin the fuel passages of the system.

A still further object of the present invention is to provide cavitationcontrol devices which are both inexpensive to manufacture and simply andeasily mounted on a fuel pump assembly.

It is a further object of the present invention to provide a cavitationcontrol device capable of refilling the fuel injection lines to eachnozzle assembly after an injection event.

Yet another object of the present invention is to provide an acavitation control device capable of regulating the fuel pressure in thefuel transfer passages during the draining event to above apredetermined minimum thereby preventing excessive cavitation.

Yet another object of the present invention is to provide a cavitationcontrol device capable of both regulating the pressure in the fueltransfer passages during the draining event while also refilling thepassages between injection events.

A still further object of the present invention is to provide a highpressure coupling having a plurality of integrally formed deliveryportions for connection to high pressure fuel lines and an orifice forcontrolling the flow through at least one of the delivery portions.

It is another object of the present invention to provide a high pressurecoupling for effectively connecting high pressure lines of a fuel systemwhile providing a convenient housing for a filter.

Another object of the present invention is to provide a high pressurecoupling which permits simple and inexpensive implementation of a rateshaping device.

Still other detailed objects of the invention may be understood byconsidering the following Summary of the Drawings and DetailedDescription of the Preferred Embodiments.

SUMMARY OF THE DRAWINGS

FIG. 1 is a schematic diagram of a fuel system assembly designed inaccordance with the subject invention.

FIG. 1a is a schematic illustration of a method for designing a specificfuel system assembly in accordance with the subject invention.

FIGS. 1b-1i are schematic illustrations of techniques for applying themethod of FIG. 1a.

FIG. 2 is an exploded perspective view of a fuel system assemblydesigned in accordance with the subject invention

FIG. 3 is an end elevational view of a fuel system assembly designed inaccordance with the subject invention.

FIG. 4 is an end elevational view of the opposite end of the fuel systemassembly of FIG. 3.

FIG. 5 is a cross sectional view of the fuel system of FIGS. 2-4.

FIG. 6 is a partial cross sectional view of the fuel system assembly ofFIGS. 2-5.

FIG. 7 is a side elevational view of an accumulator used in the fuelsystem assembly of FIGS. 2-6.

FIG. 8 is a bottom elevational view of the accumulator of FIG. 7.

FIG. 9 is an end elevational view of the accumulator of FIGS. 7 and 8.

FIGS. 10a-10l are cross sectional views of the accumulator of FIGS. 7and 8 taken along lines 10a-10l.

FIG. 11 is a side elevational view of a fuel pump housing used in thefuel system assembly of FIGS. 2-6.

FIG. 12 is a top elevational view of the fuel pump housing of FIG. 11.

FIG. 13 is a cross sectional view of the fuel pump housing of FIG. 11taken along line 13--13.

FIGS. 14-15 are cross sectional views of the fuel pump housing of FIGS.11-13 taken along lines 14--14, 15--15 and 16--16.

FIG. 17a is an end elevational view of a distributor housing used in thefuel system assembly of FIGS. 2-6.

FIG. 17b is a side elevational view of the fuel system assembly of thepresent invention showing an alternative mounting arrangement with thedistributor shaft oriented perpendicular to the pump drive shaft.

FIG. 18 is a second end elevational view of the distributor housing ofFIG. 17a.

FIG. 19 is a side elevational view of the distributor housing of FIGS.17a and 18.

FIG. 20 is a top elevational view of the distributor housing of FIGS.17a-19.

FIGS. 21 and 22 are cross sectional views of the distributor body takenalong lines 21--21 and 22--22 of FIG. 17a.

FIG. 23 is a cross sectional view of the distributor including thesolenoid operated injection control valves associated therewith takenalong line 23--23 of FIG. 20.

FIGS. 24-26 are cross sectional views of the distributor housing takenalong lines 24--24, 25--25 and 26--26 of FIGS. 20, 18 and 23respectively.

FIG. 27 is a cutaway cross sectional view of the distributor rotor andsurrounding housing taken along a plane transverse to the rotationalaxis of the rotor.

FIG. 28 is a cross sectional view of another embodiment of a fuel systemassembly designed in accordance with the subject invention.

FIG. 29 is a cross sectional view of the distributor employed in thefuel system assembly of FIG. 28 taken along line 29--29.

FIG. 30 is a cross sectional view of yet another embodiment of a fuelsystem assembly designed in accordance with the subject invention.

FIG. 31 is a cross sectional view of pump housing employed in the fuelsystem assembly of FIG. 30 taken along line 31--31.

FIG. 32 is a cross sectional view of the pump housing and accumulatoremployed in the fuel system assembly of FIG. 30 taken along line 32--32.

FIG. 33 is a partially cutaway cross sectional view of the accumulatoremployed in the fuel system assembly of FIG. 30 take along lines 33--33.

FIG. 34a is a cross sectional view of a low pressure accumulatoremployed in the fuel system assembly of FIG. 30 taken along line 34--34.

FIG. 34b is a cross sectional view of a second embodiment of the lowpressure accumulator employed in the fuel system assembly of FIG. 30taken along line 34--34.

FIG. 35 is a schematic diagram of a hydro-mechanical embodiment of thesubject invention.

FIG. 36 is a schematic diagram of yet another embodiment of a fuelsystem assembly designed in accordance with the subject invention havinga rotary pump.

FIG. 37 is a cross-sectional view of another embodiment of thedistributor of the present invention using slidable spool valves.

FIG. 38 is a cross-sectional view of the spool valve distributor of FIG.37 taken along Line 38--38.

FIG. 39 is a partial cross-sectional view of an alternative embodimentof the fuel system assembly of the present invention.

FIG. 40 is a partial cross-sectional view of yet another embodiment ofthe fuel system assembly of the present invention.

FIG. 41 is a cross-sectional view of yet another embodiment of a fuelsystem assembly designed in accordance with the subject invention.

FIG. 42 is a cross-sectional view of the fuel system assembly of FIG. 41taken generally along line 42--42.

FIG. 43 is a partial cross-sectional view of the fuel system assembly ofFIG. 42 taken generally along line 43--43.

FIG. 44 is a partial cross-sectional view of another embodiment of anaccumulator/pump housing assembly designed in accordance with thesubject invention taken along line 44--44 of FIG. 45.

FIG. 45 is a partial cross-sectional view of the accumulator/pumphousing of FIG. 44 taken along line 45--45.

FIG. 46 is a partial cross-sectional view of another embodiment of apump head/pump housing assembly used in the fuel system assembly of thesubject invention.

FIG. 47 is a partial cross-sectional view of yet another embodiment ofan accumulator/pump housing assembly used in the fuel system assemblydesigned in accordance with the subject invention.

FIG. 48 is a partial cross-sectional view of yet another embodiment of afuel system assembly designed in accordance with the subject inventionhaving vertically mounted pump control valves.

FIG. 49 is a cross-sectional view of the fuel system assembly of FIG. 48taken along line 49--49.

FIG. 50 is a cross-sectional view of the accumulator of the fuel systemassembly shown in FIG. 48 taken along line 50--50.

FIG. 51 is a cross-sectional view of the accumulator of the fuel systemassembly of FIG. 48 taken along line 51--51.

FIG. 52 is a partial cross-sectional view of another embodiment of afuel system assembly designed in accordance with the subject inventionshowing an off-mounted accumulator.

FIG. 53a is a partial cross-sectional view of the fuel system assemblyof FIG. 52 taken along line 53a--53a.

FIG. 53b is a partial cross-sectional view of another embodiment of thefuel system assembly of the present invention.

FIG. 54a is a partially cut away cross-sectional view of a feed tubehousing an edge filter connected to the accumulator of the fuel systemof the present invention.

FIG. 54b is yet another embodiment of a filter housing for mounting thefilter in the fuel system assembly of the present invention.

FIG. 55a is a partial cross-sectional view of another embodiment of thehigh pressure accumulator employed in the fuel system assembly of thepresent invention having a single end plate.

FIG. 55b is a partial cross-sectional view of yet another embodiment ofthe high pressure accumulator employed in the fuel system of the presentinvention showing two end plates.

FIG. 55c is a plan view of yet another embodiment of the high pressureaccumulator employed in the fuel system of the present invention.

FIG. 56 is a cut away cross-sectional view of a rate shaping device ofthe present invention.

FIG. 57 is a graph showing the pressure rate as a function of timeduring an injection event using the rate shaping device of FIG. 56.

FIG. 58 is a schematic diagram of another embodiment of a rate shapingdevice of the present invention.

FIG. 59 is a graph showing injection pressure as a function of time asshaped by the devices of FIGS. 58 and 60.

FIG. 60 is a schematic diagram of yet another embodiment of a rateshaping device of the present invention.

FIG. 61 is a schematic diagram of yet another embodiment of a rateshaping device of the present invention.

FIG. 62a is a cross-sectional view of a high pressure coupling of thepresent invention incorporating a filter.

FIG. 62b is a cross-sectional view of the high pressure coupling of FIG.62a taken along line 62b--62b.

FIG. 63a is a cross-sectional view of the injection control valve, boostpump and distributor used in the fuel system assembly of the presentinvention showing cavitation control devices.

FIG. 63b is a cut away cross-sectional view of the distributor of theassembly shown in FIG. 63a taken along line 63b--63b.

FIG. 64a is a cut away cross-sectional view of a cavitation controldevice of the present invention indicated at A in FIG. 63a.

FIGS. 64b-64e are partial cut away cross-sectional views of variousembodiments of cavitation control devices used in the fuel systemassembly of the present invention.

FIG. 65 is a schematic diagram of a cavitation control deviceincorporated into the fuel system assembly of the present invention.

FIG. 66 is yet another embodiment of a cavitation control deviceincorporated into the fuel system assembly of the present invention.

FIG. 67 is yet another embodiment of a cavitation control device used inthe fuel system of the present invention.

FIG. 68 is a partially cut away cross-sectional view of the distributorsimilar to FIG. 63b showing the application of the cavitation controldevice of FIG. 67.

FIG. 69 is a schematic diagram illustrating yet another embodiment of acavitation control device of the present invention used in the fuelsystem of the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the unitized fuel delivery assembly of the presentinvention is shown and may be referred to generally as the CumminsAccumulator Pump System (CAPS). As shown in schematic form and indicatedgenerally at 10, the invention includes a high pressure accumulator 12for receiving high pressure fuel for delivery to fuel injectors of anassociated engine, a high pressure pump 14 for receiving low pressurefuel from a low pressure supply pump 15 and delivering high pressurefuel to accumulator 12 and a fuel distributor 16 for providing periodicfluidic communication between accumulator 12 and each injector nozzle 11associated with a respective engine cylinder (not shown). The assemblyalso includes at least one pump control valve 18, 19 positioned alongthe fuel supply line to pump 14 for controlling the amount of fueldelivered to accumulator 12 so as to maintain a desired fuel pressure inaccumulator 12. Also, one or more injection control valves 20 positionedalong the fuel supply line from the accumulator 12 to the distributor 16is provided for controlling the timing and quantity of fuel injectedinto each engine cylinder in response to engine operating conditions. Anelectronic control module (ECU) 13 controls the operation of the pumpcontrol valves 18, 19 and the injection control valve 20 based onvarious engine operating conditions to accurately control the amount offuel delivered by the distributor 16 to the injector nozzle 11 therebyeffectively controlling fuel timing and metering.

The injection rate shape can be modified by a device located between theaccumulator and the distributor.

FIGS. 2-4 illustrate the preferred embodiment of the fuel deliveryassembly 10 in its practical form in a unitized, compact assemblyincluding an accumulator housing 34 of accumulator 12 and a distributorhousing 44 of distributor 16 both mounted on a pump housing 22associated with pump 14. As shown in FIGS. 11-16, pump housing 22includes a lower portion 23 which forms a drive shaft receiving cavity24 for radially enclosing a drive or cam shaft 26. Pump housing 22 alsoincludes an upper portion 25 integrally formed with lower portion 23 by,for example, metal casting procedures. A pair of generally cylindricalpump cavities 28 and 30 formed in upper portion 25 extend radially fromthe longitudinal axis of camshaft 26. Pump cavities 28 and 30 havegenerally parallel central axes to form an "in-line" pump configuration.Upper portion 25 of pump housing 22 includes a dividing wall 31 forseparating pump cavities 28 and 30, and a head engaging surface 32 forengaging the accumulator 12 to form an end wall for pump cavities 28 and30. Four apertures 33 are formed in upper portion 25 for receiving bolts(not shown) for securing accumulator housing 34 to pump housing 22.

Accumulator housing 34 is generally rectangularly shaped in both lateraland vertical cross-section and includes a lower surface mounted againsthead engaging surface 32 of pump housing 22. Referring to FIGS. 5-10a,four recesses 35 formed in the lower surface of accumulator housing 34opposite respective apertures 33 include internal threads for engagingcomplimentary threads formed on bolts (not illustrated) extendingupwardly from apertures 33 of pump housing 22 to connect accumulatorhousing 34 to pump housing 22. Accumulator housing 34 includes elongatedaccumulator chambers 36 extending along the axial extent of housing 34for receiving and temporarily storing high pressure fuel delivered bypump 14. Accumulator housing 34 extends axially outwardly from pumphousing 22 parallel to the longitudinal axis of camshaft 26 to form acantilevered axial overhang 38 relative to pump housing 22. Preferably,the central axis of each accumulator chamber 36 is generally parallel tothe drive axis of camshaft 26 and perpendicular to the pump axisextending in the radial direction through pump cavities 28 and 30.Accumulator housing 34 also extends laterally outwardly from pumphousing 22 to form a cantilevered lateral overhang 40. A first pumpcontrol valve 18 and a second pump control valve 19 are mounted oncantilevered lateral overhang 40 of accumulator housing 34 adjacent pumphousing 22. As illustrated in FIGS. 2, 3 and 6, pump control valves 18and 19 are received in downwardly opening recesses formed on theunderside of accumulator housing 34. In addition, a pressure sensor 42for determining the fuel pressure within accumulator chambers 36 ismounted in a recess formed on the underside of accumulator cantileveredaxial overhang 38.

Referring to FIGS. 2, 3 and 5, distributor housing 44 of fueldistributor 16 is mounted in cantilevered fashion on pump housing 22adjacent drive shaft cavity 24 and extends outwardly from pump housing22 in a spaced apart, generally parallel relationship with axialoverhang 38 of accumulator housing 34. A first injection control valve20 and second injection control valve 21 are mounted on distributorhousing 44 in the space between the distributor housing and cantileveredaxial overhang 38 of accumulator housing 34.

As described hereinabove, the various components of the unitized fueldelivery assembly 10 are oriented in a specific arrangement relative toone another so that subsequent connection of the respective housings 22,34, and 44 forms a compact, unitized assembly having outer axial, radialand lateral extents within which other components, such as pressuresensor 42, injection control valves 20 and 21, pump control valves 18and 19 and various fuel passages, can be simply and effectivelyintegrated into the assembly while maintaining the functionality of eachcomponent and the compact nature of the assembly.

Referring to FIGS. 7-9 and 10a-10l, accumulator housing 34 is formed ofan integral one piece block formed of high strength material such as SAE4340, VIMVAR quality, tempered at 700 F.; SAE 4140, VIMVAR quality,tempered to HRc 37 and gas nitrided; Maraging 18Ni(250), aged at 900 F.;Customer 455 stainless steel, aged at 950 F.; and Aermet-100, aged at900 F. Accumulator chambers 36 are formed in accumulator housing 34 byboring axial drillings in the one piece block starting at one endsurface of the block. Accumulator chambers 36 are positioned tointersect a vertical plane extending through the accumulator housing 34in a two dimensional array including an upper row 54 (FIG. 9) of fouraccumulator chambers 36a, 36b, 36c and 36d, and a lower row 56 (FIG. 9)of three accumulator chambers 36e, 36f and 36g as shown in FIG. 9. Eachaccumulator chamber 36 is elongated and cylindrical in shape andpositioned adjacent, and in generally parallel relationship with,another chamber. Also, the open end of each chamber 36 is fluidicallysealed with a plug 58 positioned in a recess 60 formed in the open end.The opposite end of each chamber 36 terminates in the block at a pointshort of the axial extent of housing 34.

Referring again to the details of the accumulator design as illustratedin FIGS. 7-9 and 10a-10l, upper row 54 of chambers 36a-d are fluidicallyinterconnected by a first cross passage 62 and an axial passage 64.First cross passage 62 extends laterally through housing 34perpendicular to the central axis of chambers 36 to intersect chambers36b-d of upper row 54. Axial passage 64 extends perpendicularly fromfirst cross passage 62 axially along housing 34 to communicate withchamber 36a which is shorter than the remaining chambers of upper row54. First cross passage 62 is formed by drilling laterally through oneside of the block to intersect chambers 36b-d of housing 34. The openend of first cross passage 62 is fluidically sealed by a plug (notshown) positioned in a recess 68 similar to plug 58 and recess 60 ofaccumulator chambers 36. Chamber 36a has been foreshortened toaccommodate recess 68. Axial passage 64 is formed by drilling from theopen end of accumulator chamber 36a prior to inserting plug 58.Likewise, accumulator chambers 36e, 36f and 36g of lower row 56 areinterconnected by a second cross passage 69 drilled from one side ofhousing 34 laterally through housing 34 terminating at chamber 36g. Aplug (not shown) is threaded into a recess 69a formed in the open end ofsecond cross passage 69 to fluidically seal passage 69. Upper row 54 andlower row 56 are connected by a vertical passage 71 and an axial passage73. Vertical passage 71 (FIG. 10b) extends upwardly from the lowersurface of cantilevered axial overhang 38 to communicate withaccumulator chamber 36a. The open end of passage 71 is fluidicallysealed by a plug (not shown) positioned in a recess formed in the openend. Axial passage 73 communicates at one end with accumulator chamber36g and at the opposite end with vertical passage 71. In this manner,first and second cross passages 62 and 69, and axial passages 64 and 73connect accumulator chambers 36a-g together to form a fluidicallyinterconnected labyrinth of chambers for temporarily storing fueldelivered from pump 14. A fuel feed passage 67 extending from the lowersurface of axial overhang 38 communicates with accumulator chamber 36d.A recess formed in the open end of fuel feed passage 67 is adapted toreceive a fuel feed tube for supplying the temporarily stored fuel tofuel injection control valves 20 and 21.

Referring to FIGS. 7, 8, 10b and 10d-10f, accumulator housing 34 alsoincludes a first pump control valve recess 70 and second pump controlvalve recess 72 formed in the lower surface of housing 34 for receivingfirst and second pump control valves 18 and 19, respectively. First andsecond pump control valves 18 and 19 are each preferably asolenoid-operated valve assembly of the type disclosed in commonlyassigned U.S. Pat. No. 4,905,960 to Barnhart incorporated herein byreference. A respective valve cavity 74,76 extends upwardly from eachpump control valve recess 70,72 respectively, but terminates belowaccumulator chamber 36a for receiving a control valve element 75 (FIG.6) of first pump control valve 18. A pair of fuel feed branches 78 and80 are formed by drilling laterally inwardly from the vertical side ofaxial overhang 38 adjacent first and second pump control valves 18 and19, respectively. The open ends of fuel feed branches 78 and 80 are eachfluidically sealed with plug (not shown) secured in a respective recessformed in the open ends. Each fuel feed branch 78, 80 communicates witha respective valve cavity 74, 76 and extends laterally through housing34 terminating at a position above the respective pump cavities 28, 30when accumulator housing 34 is mounted on pump housing 22. In addition,accumulator housing 34 is provided with a stepped recess 79 (FIG. 10i)formed in the lower surface of axial overhang 38 adjacent second pumpcontrol valve recess 72 for receiving pressure sensor 42. A passage 81connects recess 79 to accumulator chamber 36a.

Accumulator 12 also includes a first pump unit recess 82 and a secondpump unit recess 84 formed in the lower surface of housing 34 inalignment with corresponding pump cavities 28 and 30 of the pumphousing. Pump recesses 82 and 84 communicate and align with pumpcavities 28 and 30, respectively, such that respective pump units 86 and88 may be mounted within corresponding pump cavities 28 and 30 andrecesses 82 and 84 as shown in FIGS. 5 and 6. In this manner,accumulator housing 34 and respective recesses 82 and 84 form a pumphead for closing and sealing cavities 28 and 30. First and second pumpunit outlet passages 83 and 85 extend vertically through accumulatorhousing 34 connecting first and second pump unit recesses 82 and 84,respectively, to accumulator chamber 36c.

A common fuel feed passage 90 (FIGS. 5, 10b and 10e) extends laterallyinwardly from the vertical side of lateral overhang 40 between andparallel to fuel feed branches 78 and 80. A pair of connector passages92 and 94 connect common fuel feed passage 90 to pump control valverecesses 70 and 72, respectively. The opposite end of common fuel feedpassage 90 is connected to pump recesses 82 and 84 via recess drainpassages 96 and 98 (FIG. 10e) respectively for draining leak-by fuelfrom recesses 82 and 84 as further described hereinbelow. The mostinward end of each fuel feed branch 78 and 80 is connected to therespective pump unit recesses 82 and 84 by fuel passages 100 and 102,respectively (FIG. 10f). In this manner, fuel entering common fuel feedpassage 90 flows through connector passages 92 and 94 and valve recesses70 and 72 into respective fuel feed branches 78 and 80 for delivery topump units 86 and 88 via fuel passages 100 and 102 depending on theposition of the respective pump control valves 18 and 19.

Accumulator chambers 36 are specifically dimensioned to create anaggregate volume sufficient to allow a controlled quantity of fuel at apredetermined operating pressure to be delivered to each engine cylinderat appropriate times throughout the entire operating range of the enginewhile also minimizing the physical dimensions of the accumulator housing34 and ensuring that the accumulator housing walls are sufficientlystrong to withstand the forces generated by the very high operatingpressure, e.g., 5000 psi to 30,000 psi and preferably 16,000-22,000 psi,of the fuel in accumulator chambers 36. Determining the minimum requiredfuel storage volume for an accumulator designed is important in applyingthe subject invention to a particular engine. The accumulator volume isrelated to other component size choices as well. For example, the fuelquantity, timing range, injection pressure and duration required by anengine are the primary factors involved in arriving at the proper sizingof components used in designing a fuel system in accordance with thepresent invention which may be referred to as the Cummins AccumulatorPump System (CAPS). As an example, the sizing process for designing afuel system in accordance with the subject invention for the Cummins Band C engine applications is described below.

The peak nozzle pressure for this application was selected to be 21,000psi with rated duration of 30 degrees crank. The accumulator size wasestablished based on the further constraint that the maximum fuelpressure drop during an injection event should not exceed five percent.The pumping element diameter and stroke were determined by calculatingthe fuel replacement requirements in the accumulator due to fuelinjection, plus losses due to valve transition and leakage, distributorleakage, pumping element leakage, and injection line volume dumped todrain at the end of injection. Since there is one replacement pumpingevent for each injection event (the total number of cam lobes equal thenumber of engine cylinders), the total fuel loss from the varioussources during one injection should be replaced by the one pumpingevent.

A still further constraint was placed on the maximum acceptable powerloss due to leakage and other causes, based on the requirement that CAPSparasitic horsepower should not exceed that of conventional types ofprior art in-line pump designs, when operating at the same injectionpressures. Other constraints were adopted such as limiting the pumpingstroke, leakage and valve transition losses etc., limiting the size ofsealing lands for the injection control valve and distributor, and valvetransition speeds, (to avoid excessive accumulator leakage to drain). Assizing of the distributor, valve, accumulator volume, and pumpingelement stroke was determined, adequate information was available todesign the cam, bearings, tappet rollers, and pumping element springs.Finally, to determine the final CAPS hardware design, the combination ofthese elements were oriented, rearranged, examined for vehicle andengine interference and analyzed for acceptable operating stress levels.FIG. 1a schematically summarizes the design process.

With respect to the accumulator, the following information summarizesthe analytical procedure which was followed to determine the minimumrequired volume for the accumulator as applied to a fuel system designedin accordance with the subject invention for the B and C Cumminsengines:

Step 1. Calculation to determine maximum flow allowable for CAPS pumpingelements. Note: Power to support flow through the CAPS system should notsignificantly exceed conventional PLN fuel systems of the high pressure,high performance type.

Current PLN fuel systems operating at 1200 bar pump pressure require5.65 Kw drive power at 2400 rpm. Thus the drive power should not besignificantly greater for CAPS. Since the pump pressure with CAPS isnearly constant, the maximum allowable pump delivery can be calculatedfrom the following relationship for a 6 cylinder engine. ##EQU1## where:Pwr=power requirement (w)

Np=pump speed (rpm)

P=pump delivery pressure (Pa)

V=pump delivery volume (m**3)

With the design constraint that CAPS's power requirement is not toexceed 5.65 kW, this equation can be used to solve for the maximum pumpdelivery. At 1100 bar and 2400 rpm, this calculation indicates that thepump delivery should not exceed 428 mm 3/stk.

Step 2. Calculation to determine that the CAPS components do not exceedallowable flow and drive power requirements.

The pump delivery volume is the sum of the fuel volumes required forcombustion, line pressurization, and leakage. Reducing the leakage isthus critical to successful implementation of the present invention. Theleakage volumes were analyzed and reduced by design optimization. Thefollowing Table 1 lists the volume contributions to the total pumpdelivery for a Cummins C series engine.

                  TABLE 1                                                         ______________________________________                                        C Engine Pump Delivery Breakdown in mm**3 for CAPS                                         low torque torque peak                                                                             rated pwr                                   operating condition                                                                        800 rpm    1300 rpm  2400 rpm                                    ______________________________________                                        maximum fueling                                                                            150 mm3    190 mm3   155 mm3                                     line pressure                                                                              91 mm3     91 mm3    91 mm3                                      solenoid leak*                                                                             80 mm3     49 mm3    27 mm3                                      distributor leak*                                                                          150 mm3    92 mm3    50 mm3                                      pump leakage*                                                                              30 mm3     22 mm3    17 mm3                                      total        501 mm3    444 mm3   340 mm3                                     ______________________________________                                         *note:                                                                        see leakage calculation approach below.                                  

This analysis shows that the CAPS should not exceed PLN systems attorque peak through rated speeds of the same injection pressure. Atlower speeds, the pump delivery increases due to the increased timeavailable for leakage. This volume must be used for design, since highpressure capability at low speed is critical to the CAPS concept.Pumping power required at low speeds could be expected to be higher thanconventional PLN systems, when CAPS is operated at high pressure at lowspeed.

Step 3. Calculation to determine accumulator volume required to assureaccumulator pressure does not drop more than 5% between pumping events.

Determination of Accumulator Volume Requirement

Calculation of the accumulator volume required for a given pressurelevel and pressure drop during pumping was calculated as follows. Assumeuniform state, uniform flow during pumping process for one pumping eventas illustrated in FIG. 1b.

Also, it is assumed that pumping element and fuel delivery (injected+leaked) do not occur concurrently (exit mass flux is zero), adiabaticand no work done on control volume. Therefore energy equation reduces tothe following relationship for a control volume with one inlet.

    m.sub.i h.sub.i =m.sub.2 u.sub.2 -m.sub.1 u.sub.1

From conservation of mass

    m.sub.2 =m.sub.1 +m.sub.i

and thermodynamic relation ##EQU2## substitute ##EQU3## For a smallpressure drop assume density is constant, energy content of inlet massnegligible compared to energy stored in accumulator and negligibletemperature rise due to inlet fuel mass.

Therefore ##EQU4## convert to volume

    m=ρV and m.sub.i =m.sub.2 -m.sub.i =Δm ##EQU5## where: P=initial pressure

ΔV=pump volume delivery per stroke

ρ₁ =density at pressure

u₂ -u₁ =internal energy for fuel

The internal energy of diesel fuel is calculated from the relationshipfor bulk modulus as a function of pressure. ##EQU6## where: ##EQU7## B₀=bulk modulus at atmospheric B=bulk modulus at actual pressure

P=pressure

a=constant

b=constant

ρ₀ =density at atmospheric conditions

the final result follows: ##EQU8## For a given volume change, pressureand pressure drop, the volume required can be readily calculated. As thepump delivery increases the accumulator volume increases, therefore thehighest pump delivery must be used to size the accumulator. As shown,the highest pump delivery occurs at low speed due to leakage. Using thelow speed 501 mm3 pump delivery and a 5% pressure drop designconstraint, the required accumulator volume is calculated to be about130,000 mm3.

As previously indicated, the pump delivery per stroke is the sum of thecombustion, line volume pressurization and leakage fuel quantity.

    ΔV=V.sub.injected +ΔV.sub.line +ΔV.sub.slndleak +ΔV.sub.distleak +ΔV.sub.pumpleak

The line volume loss was calculated from the specific energyrelationship previously shown. Once the compression energy required toraise the total line volume to injection pressure was known, aneffective fuel volume was calculated for a constant pressure asillustrated in FIG. 1c and FIG. 1d.

Leakage for the solenoid, distributor and pumping element werecalculated using energy conservation, pressure vessel expansion formulasand diesel fuel thermodynamic properties. The clearance leakage flow canbe calculated from the following equation. ##EQU9## where: D=shaftdiameter

h=clearance

ΔP=pressure drop

μ=viscosity at temperature and pressure

L=seal length

Since the temperature profile, viscosity, pressure profile and clearanceare unknown and dependent on each other, the flow is solved iterativelyat dx intervals along the seal length assuming that the enthalpy isconstant. See FIG. 1e.

The solenoid valve is more complex due to the parallel flow that must beiterated. Also, the valve dynamics are calculated using a multi-degreeof freedom spring, mass and damper model.

Once the pump volume delivery was known, the pumping element stroke wascalculated knowing the plunger diameter. The selection of the plungerdiameter and stroke involved several iterations on hydraulic force,contact stress, bearing load, instantaneous torque, cam diameter, rollerdiameter and no follow (component inertia). All of these parameters aredependent on the plunger diameter and stroke combination. Optimizationof one parameter will most likely adversely affect other parameters. Aspreadsheet program can be used to analyze the various design options.

Determination of Accumulator Size and Shape for 130,000 mm³ AccumulatorVolume (Part I)

The CAPS package size is determined by envelope constraints of engineand vehicle components. The same gear train system in the current enginewas assumed to be suitable for driving the CAPS fuel pump. The camshaft,which transmits power from the gear train to the CAPS fuel pump, wasdetermined to be one of the constraints to locating the CAPS assembly.FIG. 1f shows the boundary constraints for the CAPS assembly as appliedto a Cummins engine.

In FIG. 1f, the right hand and bottom surfaces are limited by the engineblock. The engine size and other vehicle components constrain the lefthand and top surfaces. (These two surfaces are drawn based on the geartrain housing boundary in FIG. 1f.) The envelope length constraint isdetermined by the distance between the gear train housing and the enginefuel filter.

FIG. 1g shows how the CAPS assembly fits into the constraint envelope.In order to prevent contact with the engine block at the top corner, theentire assembly is rotated by 30° degrees when it is installed in theengine. Both side constraints and the top boundary are tight in the CAPSdesign planned for the Cummins C series engine. However, space isavailable in the longitudinal and bottom directions.

The design shown in FIG. 1g and FIG. 1h was arrived at by examiningnumerous accumulator designs. The accumulator dimensions required for asufficiently strong accumulator consisting of a single internal chamberwas determined. It was found that the length of the accumulator did notmeet the envelope requirements. The next step involved examining designswith multiple chambers with some designs involving stacked chambers. Themultiple chambers increased the width and shortened the length. Addingstacked chambers reduced the width with some height increase. Thecombination of strength, width, and length requirements were best met bythe multiple stacked chamber accumulator shown in FIG. 1h. Thedimensions identified in FIG. 1h are set forth in the following Table 2.

                  TABLE 2                                                         ______________________________________                                        Dimension    Size (mm ± .05)                                               ______________________________________                                        a            212                                                              b            106                                                              c            54                                                               d            41                                                               e            15                                                               f            15                                                               g            41                                                               h            67                                                               i            93                                                               ______________________________________                                    

The layout design of cylindrical drilling holes was based on: (1) theamount of fuel (130,000 mm³) contained inside the accumulator ascalculated using Eq. A and (2) prevention of fatigue failure duringtesting and field operation. Two rows of cylindrical drillings aredesigned to avoid the long and large holes. Hole No. 1 is shorter thanholes No. 2, 3, and 4 to ensure enough wall thickness away from the 4 mmcross hole plug seat. Bottom holes are shorter due to constraints on thepressure sensor and the fuel pump inlet. All drilling holes are designedto have a 13 mm diameter, and they are interconnected by a 4 mm crosshole or vertical side hole. The hole dimensions as shown in Table 3below are sized to have the desired fuel volume within the accumulator.

                  TABLE 3                                                         ______________________________________                                        Accumulator Drilling Hole Size                                                              Diameter   Length  Volume                                       Hole No.      (mm)       (mm)    (mm**3)                                      ______________________________________                                        1             13         164     21856.6                                      2             13         182.63  24329.4                                      3             13         182.63  24329.4                                      4             13         182.63  24329.4                                      5             13         45.5     6127.8                                      6             13         80.5    10773.4                                      7             13         89.5    11968                                        Total                            123713.9                                     Accumulator approx.                18.82                                      total weight (lbs):                                                           ______________________________________                                    

The wall thickness around holes is determined so that the stresses atstress concentrations are less than the allowable material strength toprevent fatigue failure. The pressure vessel formula as well as detailedfinite element analysis are used to estimate the stress levels. Sincethe stress concentration at drilling hole intersections is a majorconcern in the accumulator design, the detail finite element analysiswould provide adequate local stress results. It is known that the stressconcentration factor for closed end cylinders with side holes or crossholes is typically from 3.0 to 4.0. For example, the stressconcentration factor in Peterson's book is 3.42 for the holes size givenin Table 4.

The analytical pressure vessel formula for the maximum tensile stressσ_(t) in the circumferential direction is

    σ.sub.t =p(b.sup.2 +a.sup.2)/(b.sup.2 -a.sup.2)      (1)

where p is the internal radial pressure, a is the cylinder inner radius,and b is the cylinder outer radius. The cylinder wall thickness t iscalculated by t=b-a. Note that Eq. (1) is accurate for cylindrical thickvessels without intersecting drillings. Also, the effect of closed endcap is not considered.

The objective is to find out the minimum wall thickness for a givenoperating pressure, drilling hole diameter, and material properties.Five materials were considered for prototype accumulator fabrication.They were:

1. SAE 4340, VIMVAR quality, tempered at 700 F.

2. SAE 4140, VIMVAR quality, tempered to HRc 37 & gas nitrided.

3. Maraging 18Ni(250), aged at 900 F.

4. Customer 455 stainless steel, aged at 950 F.

5. Aermet-100, aged at 900 F.

Table 4 below shows the wall thickness requirement for various materialsand stress intensification factors (SIF) at the drilling intersection.In Table 4, the material allowable tensile stress is calculated from theGoodman diagram for R=O. The stress intensification factor at thedrilling hole intersection depends on the hole diameter, intersectionangle, hole offset, radius at intersection corner, etc., and the SIF isgiven as a design input data in Table 4. The allowable maximum tensilestress inside the pressure vessel is the material allowable tensilestress divided by the stress intensification factor. The accumulatordrawing shown in FIG. 4B has a 6.5 mm minimum wall thickness. Withresults calculated in Table 4, it is concluded that the wall thicknessaround the holes is adequate for the selected material in theaccumulator design.

                                      TABLE 4                                     __________________________________________________________________________    Sizing the Accumulator Wall Thickness                                         Drilling      Material Strength                                                                     Allow. Tensile                                                                             Allow. Max.                                Hole                                                                              Operation Ult. Str.                                                                         Edn Str.                                                                          Str. from                                                                            Estimated                                                                           Cylind. Tensile                                                                      Min. Wall                           Radius                                                                            Pressure*                                                                          Acm. Su  Se**                                                                              GDM R = 0                                                                            SIF @ drill                                                                         Str. [Sa/SIF]                                                                        Thickness                           (mm)                                                                              (ksi)                                                                              Material                                                                           (ksi)                                                                             (ksi)                                                                             Sa (ksi)                                                                             intersec.                                                                           (ksi)  (mm)                                __________________________________________________________________________    6.5 19.575                                                                             SAE 4340                                                                           270 80.64                                                                             124.189                                                                              2.5   49.676 3.359                               6.5 19.575                                                                             SAE 4340                                                                           270 80.64                                                                             124.189                                                                              3     41.396 4.365                               6.5 19.575                                                                             SAE 4340                                                                           270 80.64                                                                             124.189                                                                              3.42  36.313 5.377                               6.5 19.575                                                                             SAE 4340                                                                           270 80.64                                                                             124.189                                                                              4     31.047 7.154                               6.5 19.575                                                                             AM-100                                                                             280 115.2                                                                             163.239                                                                              2.5   65.296 2.356                               6.5 19.575                                                                             AM-100                                                                             280 115.2                                                                             163.239                                                                              3     54.413 2.973                               6.5 19.575                                                                             AM-100                                                                             280 115.2                                                                             163.239                                                                              3.42  47.731 3.55                                6.5 19.575                                                                             AM-100                                                                             280 115.2                                                                             163.239                                                                              4     40.81  4.461                               __________________________________________________________________________     Note: *Operation pressure 1350 bar = 19.575 ksi.                              **A 0.72 surface finish factor is included in the endurance strength.    

In the study of stresses at the drilling hole intersection, thefollowing two types of loadings are considered.

Condition 1: A significant number of engine start-up/shut down cyclesoccur throughout the accumulator life. This results in an estimated25,000 pressure cycles in the accumulator from 0 to 1100 bar.

Condition 2: Small pressure fluctuations occur in the accumulatorcylinders during operation. A maximum pressure drop of 15% from themaximum pressure level (1100 bar) is assumed. These pressurefluctuations from 935 to 1100 bar are anticipated to occur 10⁸ -10⁹cycles.

A 3-D finite element model is shown in FIG. 1i. The model has 1168elements and 1566 nodes. The analysis results are summarized in Table 5.The stress intensification factor ranging from 3.0 to 4.4. is estimatedfor various hole size. The Aermet-100 material properties are used tocalculate the fatigue margin in Table 5. The analysis results in Table 5show the accumulator has excellent structural integrity if the operatingpressure condition does not exceed 1100 bar. Also, abrasive flowmachining is recommended to improve intersection geometry and keepstress concentrations to a minimum, thereby preventing fatigue failures.

                                      TABLE 5                                     __________________________________________________________________________    Stress Analysis Results of Accumulator Drilling Hole Intersections            Cylnd. Hole                                                                         Cross Hole                                                                          Operation                                                                          Intersec. Nominal                                                                            Max. Stress                                   Diam. Diam. Pressure                                                                           Radius                                                                             Closed                                                                             Stress                                                                             Tens. Str                                                                          Intens. Fact.                                                                       Fatigue Margin**                   (mm)  (mm)  (ksi)                                                                              (mm) End Cap                                                                            (ksi)                                                                              (ksi)                                                                              Smax/Snom                                                                           Cond. 1                                                                           Cond. 2                        __________________________________________________________________________    13    3     15.95                                                                              Square                                                                             no   17.744                                                                             78   4.4   54% 82%                            13    4     15.95                                                                              Square                                                                             no   19.286                                                                             81   4.2   53% 81%                            13    4     15.95                                                                              Square                                                                             yes  19.286                                                                             82   4.25  52% 81%                            13    4     15.95                                                                              0.5  yes  19.286                                                                             78   4.04  54% 82%                            13    8     15.95                                                                              Square                                                                             no   35.394                                                                             107  3.02  33% 71%                            __________________________________________________________________________     Note: *1100 bar = 15.95 ksi.                                                  **The material Aermet  100 is used to estimate the fatigue margin.       

Reference will now be made to the details of the pump assembly. Inparticular, the pump units 86 and 88 will now be described in detailwith reference to FIGS. 5 and 6. Pump units 86 and 88 of pump 14 arestructurally the same and, therefore, only pump unit 86 will bedescribed hereinbelow. Pump unit 86 includes a pump retainer 104positioned in pump unit recess 82 and extending outwardly towardcamshaft cavity 24. Pump retainer 104 is generally cylindrical in shapeto form a cavity 105 and includes an upper portion 106 having externalthreads for engaging complementary threads formed on the inner surfaceof pump unit recess 82. Retainer 104 also includes a smaller diameterlower portion 108 extending into pump cavity 28 and terminating to forma lower wall 110. Pump unit 86 also includes a disk 112 positionedwithin cavity 105 and pump unit recess 82 and a pump barrel 116 mountedadjacent disk 112 in cavity 105 of retainer 104. Retainer 104 holdsbarrel 116 and disk 112 in a compressive abutting relationship with disk112 forced against accumulator housing 34 when retainer 104 is fullythreaded into recess 82. A center bore 118 extending throughout theentire length of pump barrel 116 is aligned with a central opening 120in lower wall 110 of retainer 104. A pump plunger 122 is mounted forreciprocal movement in central bore 118 and central opening 120 to forma pump chamber 124 between the upper end of plunger 122 and disk 112which forms an end wall 114 for pump chamber 124. Thus, retainer 104permits pump units 86 to be mounted in pump unit recess 82 ofaccumulator housing 34 and extend into pump cavity 28 of pump housing 22without directly contacting pump housing 22. This arrangement limits thehigh pressure sealing surfaces to the contact areas between the disk 112and recess 82, and disk 112 and barrel 116, thereby avoiding the needfor sealing surfaces on pump housing 22. Also, retainer 104 can beinexpensively and easily machined as a replacement part with theappropriate dimensions to correspond to the dimensions of recess 82 ofaccumulator housing 34.

An annular disk groove 126 formed in the upper surface of disk 112adjacent housing 34 communicates with respective fuel passage 100. Apair of axial disk inlet passages 128 extend from annular disk groove126 on opposite sides to connect with pump chamber 124. A disk outletpassage 130 extending through the center of disk 112 is aligned with acheck valve recess 132 formed in accumulator housing 34 adjacent disk112. Pump unit outlet passage 83 extends from check valve recess 132through accumulator housing 34 to connect with accumulator chamber 36c.A pump unit check valve 136 is positioned in check valve recess 132 andadapted to sealingly engage the upper annular surface of disk 112surrounding outlet passage 130 to prevent the flow of high pressure fuelfrom chamber 36c when the pressure of the fuel in chamber 36c is greaterthan the pressure of the fuel in pump chamber 124 while permitting fuelflow from chamber 124 into accumulator 36c when the pressure in pumpchamber 124 exceeds the fuel pressure in accumulator chamber 36c.

Respective recess drain passage 96 extending from common fuel passage 90communicates with an annular recess clearance 138 formed between theannular top surface of pump retainer 104 and accumulator housing 34. Apump unit clearance 140 formed between both pump disk 112 and retainer104, and barrel 116 and retainer 104, communicates at all times withrecess clearance 138. A retainer drain passage 142 formed in barrel 116extends radially outwardly from central bore 118 to communicate withpump unit clearance 140 adjacent lower portion 108 of retainer 104. Anannular drain groove 144 formed in pump plunger 122 intermittentlycommunicates with drain passage 142 during reciprocation of pump plunger122. Fuel leaked from pump chamber 124 between barrel 116 and plunger122 collects in drain groove 144 and intermittently drains into drainpassage 142. Fuel from drain passage 142 is continuously drained throughpump unit clearance 140, recess clearance 138 and recess drain passage96 into common fuel feed passage 90.

As shown in FIGS. 5 and 6, the lower end of pump plunger 122 extendsthrough lower wall 110 of retainer 104 to engage a button 146 of atappet assembly 148. Button 146 includes an upper semi-spherical seatingsurface for engaging a complementary semi-spherical surface formed onthe lower end of pump plunger 122. Tappet assembly 148 also includes atappet housing 150 having a cylindrical outer surface mounted forreciprocable movement against corresponding cylindrical tappet guidingsurfaces 152 formed on a portion of the vertical interior walls of pumphousing 22. Tappet guiding surfaces 152 are machined to ensure smoothsliding contact between tappet housing 150 and pump housing 22 ashousing 150 reciprocates. A lower spring seat 154 positioned aroundbutton 146 and the lower end of plunger 122 engages both button 146 anda retaining ring 156 positioned in an annular groove 157 formed onplunger 122. A bias spring 158 positioned around lower portion 108 ofretainer 104 engages, at one end, a step 160 formed between upperportion 106 and lower portion 108 of retainer 104. The opposite end ofbias spring 158 extends through pump cavity 28 to engage lower springseat 154 thereby biasing tappet assembly 148 and plunger 122 towardcamshaft 26. A roller 162 including a central bore 164 is positioned inan interior cavity 166 formed in tappet housing 150. Roller 162 isrotatably secured to housing 150 by a pin 168 extending through bore 164into apertures 170 formed in tappet housing 150 on opposite sides ofcavity 166. Therefore, each roller 162 associated with each tappethousing 150 is biased by spring 158 against a respective cam 172 formedon camshaft 26.

Cams 172 are positioned in camshaft cavity 24 between a first opening200 and a second opening 202 formed in lower portion 23 of pump housing22. Camshaft 26 is secured to an engine shaft (not shown) by a woodruffkey 173 or any other conventional means for securing two rotating shaftstogether. Camshaft 26 rotates at a speed half of the engine speed torotate each cam 172 360 degrees for every 720 degrees rotation of theengine crankshaft. Each cam 172 includes at least one lobe 204 forcausing the associated pump plunger 122 to undergo one advancing orpumping stroke and one return stroke for each revolution of thecamshaft. However, in order to supply, maintain and control the highfuel pressure in accumulator chambers 36, it is advantageous toreplenish fuel in the accumulator chambers 36 in synchronism with theremoval of fuel from accumulator chambers 36. To accomplish thissequential operation, the number of advancing strokes must equal thenumbers of engine cylinders. In the six-cylinder engine of the preferredembodiment, two pump units 86 and 88 are each driven by a respective cam172 provided with three lobes 204 so that the total number of lobes and,therefore, the total number of advancing strokes equals the number ofengine cylinders, i.e. six. In this manner, each advancing stroke ofpump plungers 122 corresponds directly in time to a delivery periodassociated with fuel distributor 16 and, therefore, an injection periodof an injector (not shown). Therefore, lobes 204 are positioned aroundeach cam 172 to permit a fuel pulse to be supplied to accumulatorchambers 36 by pump units 86 and 88 during the same period in which afuel pulse is removed from accumulator chambers 36 for delivery to theinjectors by distributor 16.

During the operation of pump 14, pump control valves 18 and 19 arenormally de-energized in an open position. Thus, during the retractionstroke of each pump plunger 122, fuel flows from common fuel feedpassage 90 through respective fuel feed branches 78 and 80 intorespective pump chambers 124. Also, during the pumping or advancingstroke, each pump plunger 122 forces fuel out of its respective pumpchamber 124 back through fuel feed branches 78 and 80 and respectivepump control valves 18 and 19. However, when the fuel pressure inaccumulator chambers 36 falls below a predetermined minimum, ECU 13 willenergize pump control valves 18 and 19 as needed at a predeterminedpoint during the a respective pumping stroke of pump plungers 122 thusclosing the respective pump control valve 18, 19 blocking the flow offuel from the respective pump chamber 124. Further advancement of pumpplunger 122 pressurizes the fuel in pump chamber 124 until the fuelpressure in chamber 124 exceeds the fuel pressure in accumulatorchambers 36 causing pump unit check valve 136 to lift off its seatallowing fuel from pump chamber 124 to flow into accumulator chambers 36thereby maintaining the fuel pressure in accumulator 12 within a desiredpressure range. The discharge of fuel from chamber 124 into accumulator12 ends when pump plunger 122 finishes its advancing or pumping stroke.In this manner, the pump 14 and associated pump control valves 18 and 19are operated to control the effective displacement of each pump chamber124 by providing a variable beginning of injection upon closure of arespective pump control valve 18, 19 while a constant end of injectionoccurs when the pumping plunger 122 reaches its top dead center or mostadvanced position. However, other forms of variable displacement highpressure pumps may be used to control accumulator pressure. Examples ofsuch other variable displacement pumps are disclosed in U.S. Pat. No.4,502,445 to Roca-Nierga et al. and in a co-pending patent applicationfiled on the same date as the present application and entitled VariableDisplacement High Pressure Pump for Common Rail Fuel Injection Systemsin the name of Yen et al. and assigned to the assignee of thisinvention. The entire disclosure of that application is incorporatedherein by reference.

Referring to FIGS. 5 and 17a-27, fuel distributor housing 44 ofdistributor 16 is mounted on lower portion 23 of pump housing 22adjacent second opening 202. Fuel distributor housing 44 includes arotor bore 214 extending axially through housing 44 in axial alignmentwith second opening 202 of pump housing 22. An annular seal recess 206is formed in distributor housing 44 at one end of rotor bore 214 forreceiving shaft seals 208 which prevent fuel leaking form around rotor216 from entering camshaft cavity 24. A rotor 216 is rotatably mountedin rotor bore 214 and connected at a first end to camshaft 26 by acoupling 218. A second end of rotor 216 terminates adjacent the innersurface of a recess 220 formed in the end of distributor housing 44adjacent rotor bore 214 (FIGS. 5, 22 and 25). Recess 220 includesinternal threads for engaging the external threads of a drain fitting222 having a drain port 224 extending axially therethrough. Althoughdistributor housing 44 preferably extends axially from pump housing 22,housing 44 may be mounted on pump housing 22 so that rotor 216 extendsperpendicular to the axis of camshaft 26 as shown in schematic form inFIG. 17b. In this arrangement, rotor 216 may be operatively connected tocamshaft 26 by gears 217.

Rotor 216 includes an axial supply passage 226 extending axially along,but radially spaced from, the central axis of rotation of rotor 216 fromthe second end of rotor 216 inwardly terminating at a point prior to thefirst end (FIGS. 5 and 27). A plug 228 is threadably secured in the openend of axial supply passage 226 adjacent recess 220 to fluidically sealpassage 226 from drain port 224. A radial supply passage 230 extendsradially from axial supply passage 226 to communicate with rotor bore214. Six fuel receiving ports 231 and six corresponding fuel receivingpassages 232 are formed in distributor housing 44 and equally spacedaround the circumference of rotor bore 214 for successive communicationwith radial supply passage 230 during rotation of rotor 216. Asemi-annular balance groove 234 formed in rotor 216 extends aroundapproximately 75% or 272° of the circumference of rotor 216. Balancegroove 234 terminates on either side of radial supply passage 230 suchthat when supply passage 230 registers with one of the receivingpassages 232, the remaining receiving passages 232 communicate withbalance groove 234. Therefore, the fuel pressure in the receivingpassages 232 communicating with balance groove 234 will be equalizedbefore the start of each injection period. This balancing orequalization of the initial fuel pressure in receiving passages 232 andcorresponding downstream passages insures controllable and predictablefuel metering from one injection period or engine cycle to the next.Moreover, an axial drain passage 233 formed in rotor 216 extendsinwardly from the end of the rotor 216 adjacent drain fitting 222 tocommunicate with a radial passage 235 extending radially inward frombalance groove 234. In this manner, the fuel in balance groove 234 and,therefore, the receiving passages 232 not communicating with radialsupply passage 230, is continuously connected to the fuel drain which ismaintained at a relatively constant low pressure. As a result, eachreceiving passage 232 is maintained at a relatively predictable,constant pressure so that the pressurization of each receiving passage232 begins at approximately the same pressure thus improvingcontrollability and predictability of fuel metering. The opposite end ofeach receiving passage 232 communicates with a recess 236 formed in theend of distributor housing 210. Each recess 236 has internal threads forengaging complementary external threads on an outlet fitting 238. Anaxial injection bore 240 extends axially through each outlet fitting 238to communicate with a respective receiving passage 232. Receivingpassages 232 are formed by drilling inwardly through distributor housing44 from each recess 236 at an acute angle to the rotor axis. In thismanner, each outlet fitting 238 fluidically seals the portion of thedrilling radially outward of fitting 238 thereby providing a fluidicallysealed connection between each receiving passage 232 and each injectionbore 240. A radial receiving passage 242 formed in rotor 216 and axiallyspaced from radial supply passage 230 extends radially outwardly fromaxial supply passage 226 to communicate with an annular supply groove244.

The portion of the present fuel delivery system for delivering fuel fromaccumulator chambers 36 to supply groove 244 will now be described indetail. As shown in FIG. 5, fuel is delivered from accumulator chamber36a to distributor housing 44 via fuel feed passage 67 and a fuel feedtube 246. A feed supply recess 248 formed in the open end of feedpassage 67 includes a feed tube seat 250 for engaging a feed tube head252 formed on the end of feed tube 246. Supply recess 248 includesinternal threads for engaging complementary external threads formed on agenerally cylindrical feed tube fitting 254. Feed tube 246 extendsthrough tube fitting 254 so that one end of tube fitting 254 abuts tubehead 252. Rotation of tube fitting 254 relative to supply recess 248 andfuel feed tube 246 forces feed tube head 252 inwardly into sealingengagement with tube seat 250 thereby creating a fluidically sealedconnection between feed passage 67 and feed tube 246. Feed tube 246extends downwardly in the space between distributor housing 44 andcantilevered axial overhang 38 of accumulator housing 34 into a feedtube receiving recess 256 formed in the upper surface of distributorhousing 44. A cylindrical seal 258 formed on the end of feed tube 246 isforced radially outwardly against the surface of receiving recess 256 toprevent fuel from leaking between feed tube 246 and receiving recess256. An annular seal groove 260 formed in recess 256 is adapted toreceive a seal for preventing leakage of fuel out of recess 256 betweenfeed tube 246 and housing 44. An annular feed tube drain groove 262formed in recess 256 between seal groove 260 and cylindrical seal 258collects any fuel leaking upwardly in recess 256 between feed tube 246and housing 44. A drain passage 263 extends from drain groove 262 toconnect with the drain system from first injection control valve 20.

An axial feed bore 264 extends from the transverse face of distributorhousing 44 adjacent second opening 202 of pump housing 22 axiallyoutwardly to communicate with a first injection control valve cavity 270formed in distributor housing 44 for receiving first injection controlvalve 20 (FIG. 24). Axial feed bore 264 continues from first injectioncontrol valve cavity 270 axially outwardly to communicate a passage 266extending from recess 256. The open end of transverse bore 264 includesa recess 268 fluidically sealed with a plug (not shown). A secondinjection control valve cavity 272 is formed in distributor housing 44adjacent first injection control valve cavity 270 so that first andsecond injection control valve cavities 270 and 272, respectively, arelocated on opposite transverse sides of rotor 216. A transverse feedbore 274 extending from one side of distributor housing 44 above rotor216 fluidically connects first injection control valve cavity 270 withsecond injection control valve cavity 272 (FIGS. 21 and 23). Transversefeed bore 274 and axial feed bore 264 are formed in the same horizontalplane so as to intersect first injection control valve cavity 270 atadjacent points around the circumference of cavity 270. The open end oftransverse feed bore 274 is fluidically sealed with a plug 275 (FIG.23). A rotor feed bore 276 formed in distributor housing 44 extends fromone side of housing 44 below rotor 216 to communicate with a firstoutlet passage 278 and second outlet passage 280 extending from firstand second injection control valve cavities 270 and 272, respectively(FIGS. 19, 23-26). The open end of rotor feed bore 276 is fluidicallysealed with an appropriately sized plug similar to plug 277. A rotorport 282 extends vertically upward from rotor feed bore 276 tocommunicate with rotor bore 214. Feed port 282 is formed by drillingupwardly through the bottom of distributor housing 44. Therefore, theopen end of the drilling associated with feed port 282 is fluidicallysealed with a plug (not shown).

Feed port 282 and rotor feed bore 276 are formed in a common verticaltransverse plane with radial receiving passage 242 and supply groove 244so that feed port 282 continuously communicates with supply groove 244and radial receiving passage 242 as rotor 216 rotates. As a result, fueldelivery to axial supply passage 226 via radial receiving passage 242,supply groove 244, feed port 282, rotor feed bore 276 and first andsecond outlet passages 278 and 280 from transverse bore 274 is dependentonly on the position of the respective injection control valves 20 and21. However, a two way check valve is positioned in rotor feed bore 276to prevent fuel supplied from one of the injection control valvecavities 270 and 272 to flow into the other injection control valvecavity. First and second injection control valves 20 and 21, which areeach operable to connect axial supply passage 226 with accumulatorchamber 36a, may be of the three way type illustrated in FIG. 23 anddescribed in detail in a co-pending patent application filed on Mar. 19,1993 entitled Force Balanced Three-Way Solenoid Valve in the name ofPataki et al. and assigned to the assignee of this invention. The entiredisclosure of that application is incorporated herein by reference.

First and second injection control valves 20 and 21 are also operable tofluidically connect axial supply passage 226 with a low pressure fueldrain circuit indicated generally at 284 (FIG. 22). Drain circuit 284includes a first and a second axial drain passage 286 and 288,respectively, extending axially from the transverse face of distributorhousing 44 adjacent pump housing 22 to communicate with first and secondinjection valve cavities 270 and 272, respectively. Axial drain passages286 and 288 also extend axially from respective cavities 270 and 272 tocommunicate with drain passageways 290 and 292, respectively (FIG. 22).Drain passageways 290 and 292 each extend inwardly at an angle towardthe axis of rotor 216 to communicate with an annular drain collectiongroove 294 formed in recess 220. A pair of drain apertures 296 and 298formed in the innermost end of each drain fitting 222 extend from draincollection groove 294 to drain port 224 to direct fuel from draincollection groove 294 to a low pressure fuel drain connected to theopposite end of drain fitting 222 (FIG. 5).

Drain circuit 284 further includes an axially extending drain passage300 formed in distributor housing 44 to communicate with seal recess 206at one end and drain passageway 292 at an opposite end (FIG. 17a, 22 and23). Therefore, any fuel leaking into seal recess 206 from the clearancebetween rotor 216 and distributor housing 44 is directed to drain. Avertical drain passage 302 communicates at one end with a second valverecess 304 formed at the upper end of valve cavity 272 and at a secondend with axial drain passage 288. A first valve recess 306 isfluidically connected to second valve recess 304 by a pair of drainpassages 308 and 310, each extending inwardly from respective recesses306 and 304 (FIG. 20 and 23). As a result, any fuel leaking from valvecavities 270 and 272 is collected in recess 306 and 304, respectively,and directed to drain by vertical drain passage 302, axial drain passage288, drain passageway 292, drain aperture 298 and drain port 224.

Referring to FIG. 5, a safety valve 312, shown in schematic form, ispositioned along the fuel transfer circuit in feed tube 246 between theaccumulator 12 and injection control valve 20. During operation of thefuel pump system, injection control valve 20 may become unintentionallyjammed or lodged in the open position continuously fluidicallyconnecting accumulator 12 to distributor 16. As a result, high pressurefuel from accumulator 12 will be permitted to flow through distributor16 to the engine cylinders during the entire time of each injectionperiod. Thus, regardless of the engine throttle position, fuel isundesirably continuously supplied to the engine resulting, possibly, inan engine run-away condition. Safety valve 312 prevents such a run-awaycondition by blocking fuel flow to distributor 16 when injection controlvalve 20 improperly remains in the open position. Safety valve 312 maybe a pressure balanced two-way, two-position solenoid-operated valvewhich completely blocks fuel flow through feed tube 246. Alternatively,safety valve 312 may be a pressure balanced three-way valve, similar toinjection control valve 20, movable from an open position permittingflow from accumulator 12 to distributor 16 under normal operatingconditions into a drain position blocking flow to distributor 16 whileconnecting accumulator 12 via feed tube 246 to a drain passage 314.Safety valve 312 may be controlled by a signal from an ECU (not shown)indicating that injection control valve 20, upon receiving a closingsignal, failed to reach the closed position. In addition, safety controlvalve 312 may alternatively be positioned within the fuel transfercircuit between injection control valve 20 and distributor 16.

Reference is now made to an alternative embodiment of the subjectinvention as illustrated in FIG. 28. In this embodiment, the same basiccomponents referred to with respect to the first embodiment of FIGS. 2-6are illustrated, namely, a pump 401, accumulator 402 and distributor404. Unlike the previous embodiment, however, the fuel pump assembly 400of FIG. 28 includes a gear type boost pump 406 located in acomplementary cavity 408 contained in the distributor housing 410. Thepurpose of boost pump 406 is to insure that the pump chambers 412 and414 are filled with fuel during the downward stroke of the respectivepump plungers 416 and 418. During certain operating conditions, such ashigh engine speeds, the downward stroke of pump plunger 416 and 418 willoccur at a rate that exceeds the capacity of the normal engine "lift"pump to cause fuel to fill the respective pump chambers 412 and 414.

To remedy the problem associated with the pump chambers failing to befully charged at all times, boost pump 406 is provided to raisesignificantly the pressure of the fuel supplied to chambers 412 and 414.For example, boost pump 406 may raise the supply pressure of the fuelsupplied to the pump chambers from a low level, for example 5 psi, tosignificantly higher level, for example 200-300 psi. This significantlyhigher pressure will generally assure that chambers 412 and 414 will befully charged with fuel even during periods of maximum downward velocityof the corresponding pump plungers 416 and 418.

Pump 406 includes a pair of intermeshing gears 420 and 422 received incavity 408. Gear 422 is mounted on a shaft 424 which is co-axial withand connected for driving rotation with the drive shaft of the pump 401.The other end of shaft 424 is connected to a distributor rotor 425 whichfunctions similarly to rotor 216 of the FIG. 5 embodiment. A spacerhousing 426 is positioned between pump housing 428 and distributorhousing 410 to facilitate assembly of the distributor and boost pump onthe pump housing 428. A bearing journal 430 is provided in spacerhousing 426 for one end of shaft 424. A fluid seal ring 432 may beprovided surrounding one end of driving shaft to maintain the separationof fuel in the boost pump and the lubrication fluid in the drive shaftcavity 434 of the high pressure pump 401.

The high pressure fuel is stored in accumulator 402 for supply to thedistributor 404 through a feed tube 436. Although not shown in FIG. 28,passages internal to distributor housing 410 are provided to providehigh pressure fuel to the axial supply passage 438 in rotor 425 forsequential communication to the individual engine cylinders in themanner previously described. A pair of solenoid operated injectioncontrol valves 440 (only one of which is visible in FIG. 28) areprovided to control the timing and quantity of fuel injection into eachengine cylinder by controlling the flow of fuel from feed tube 436 intothe axial supply passage 438. Injection control valves 440 may also beof the three way type illustrated in FIG. 23 and described in detail ina co-pending patent application filed on Mar. 19, 1993 entitled ForceBalanced Three-Way Solenoid Valve in the name of Pataki et al. andassigned to the assignee of this invention.

An alternative type of solenoid operated, injection control valve 440 isillustrated in FIG. 29. A pair of such valves 440 and 440' isillustrated in FIG. 29 as they would appear in a transverse crosssection of the distributor 404 taken along lines 29--29 of FIG. 28. Thistype of valve is characterized by the provision of a "pin-in-sleeve"valve member which is force balanced but which includes a high pressurevalve seat 442 which is considerably smaller in effective seal area thanis the drain valve seat 444. When valve 440 is actuated, supply passage446 is connected through valve seat 442 of the three way valve with afeed bore 448 which in turn communicates with the rotor receiving bore450 through a connecting passage 452. The advantage of this type ofvalve is that the flow characteristics of the valve upon opening can bemade considerably different than the flow characteristics upon closing.Also, a two way check valve 453 is positioned in feed bore 448 toprevent fuel supplied from one of the injection control valve cavitiesto flow into the other injection control valve cavity. This style ofthree way control valve is also described in greater detail in theco-pending patent application filed on Mar. 19, 1993 entitled ForceBalanced Three-Way Solenoid Valve in the name of Pataki et al. andassigned to the assignee of this invention.

Reference is now made to FIG. 30 which discloses yet another embodimentof the subject invention. In this embodiment, a single solenoidoperated, three way injection control valve 454 is provided in place ofthe dual three way valves of FIG. 23 or FIG. 29. In particular,injection control valve 454 includes its own valve housing 456containing a valve cavity 460 in which is received a three way valve ofthe type illustrated in FIG. 29. Unlike the injection control valves ofFIGS. 23 and 29, however, injection control valve 454 is oriented withthe central axis of valve cavity 460 parallel to the rotational axis ofthe distributor rotor 462 of the distributor 464. High pressure fuelfrom the accumulator 466 is supplied through a feed tube 468 to thevalve cavity 460. When the solenoid 470 is actuated, the valve member472 moves to the right in FIG. 30 to connect feed tube 468 to passage474 which in turn supplies the high pressure fuel to the distributorbore 475 through passage 476.

FIG. 30 also discloses a spacer housing 478 which differs from thespacer housing illustrated in FIG. 28 by provision of a low pressureaccumulator 480. The purpose of this additional accumulator is to permitan adequate volume of fuel to be available for supply to the pumpchambers 482 and 484 of the high pressure pump 486 even during the timeof highest retraction velocity of pump plungers 490 and 492. Without lowpressure accumulator 480, the size of the gear pump would need to begreater to handle the high flow rate required during the period ofgreatest downward retraction velocity of plungers 490 and 492. Fuel flowproceeds through the fuel pump assembly as follows: Fuel is supplied tothe assembly from a fuel source, such as a fuel tank (not shown), to thegear pump 494 contained in a separate gear pump housing 495. From thegear pump the fuel is provided to the low pressure accumulator 480through a first transfer passage 496 (shown schematically in dashedlines) and from low pressure accumulator to a supply passage 498contained in the high pressure accumulator 466 through a series ofpassages contained in the spacer housing 478, pump housing 500 andaccumulator 466. More particularly, the outflow of fuel from the lowpressure accumulator 480 is supplied to the pump housing 500 through asecond transfer passage 502.

Reference is now made to FIG. 31 which is a cross-sectional view of thepump housing 500 taken along lines 31--31 of FIG. 30. Fuel from secondtransfer passage 502 is received in a horizontal passage 504 andtransferred up through vertical passage 506 for communication withsupply passage of accumulator 466 through an accumulator transferpassage 508 as illustrated in FIG. 32 which is a cross section of thepump housing 500 and accumulator 466 taken along lines 32--32 of FIG.30. From supply passage 498, fuel flows to the pump control valverecesses 510 and 512 through passages 514 and 516, respectively, asillustrated in FIG. 33 which is a broken away cross sectional view ofthe accumulator 466 taken along lines 33--33 of FIG. 30. Unlike thepassages shown in FIG. 10e, supply passage 498 is blocked at 518 (FIGS.32 and 33) so that fuel leakage returned to the supply passage 498through passages 520 and 522 from pump units illustrated in FIG. 30,does not mix with the fuel supplied to the pump control valves. Instead,as illustrated in FIGS. 31, 32 and 33, fuel is returned to the lowpressure intake of gear pump 494 in pump housing 495 through a series ofpassages labeled 524, 526, 527 and passages not illustrated formed inspacer housing 478 and 495.

A series of drain passages are also provided in the injection controlvalve housing 456, the distributor housing 528, and the gear pump shafts530 and 532. Namely these passages include a drain passage 534 extendingradially through valve housing 456 to direct fuel drains from injectioncontrol valve 454 to an annular drain passage 536 formed in the topsurface of distributor 464 which also collects leakage from the highpressure connection of passages 474 and 476. A drain passage 538 extendsinwardly from passage 536 to connect with an annular cavity 539 formedaround one end of distributor rotor 462 which also receives fuel leakagefrom between rotor 462 and distributor housing 528. Annular cavity 539is connected to the intake of gear pump 494 by drain passages 541 and543. Passage 541 also communicates with a drain cavity 544 whichcollects fuel leakage from between rotor 462 and housing 528 via drainpassages 546 and 548. Also, a drain passage 550 extends from an annularcavity 552 formed between lip seals 554 positioned around one end ofcrankshaft 556 to drain fuel collecting in cavity 552 to a drain notshown. In addition, a pair of drain passages 540 and 542 extendingaxially through gear pump shafts 530 and 532, respectively, collect fuelleaking between gear pump shafts 530 and 532 and spacer housing 478.Passage 542 directs fuel leakage to cavity 544 while passage 540 directsfuel leakage to cavity 539. A check valve 545 positioned in passage 540is biased to prevent the flow of leakage fuel to the right in FIG. 30until a low fluid pressure, e.g. 5 psi, is reached in passage 540. Thisarrangement prevents gear pump 494 from drawing air into its intake frompassage 550 and camshaft cavity 558.

Reference is now made to FIG. 34a and FIG. 34b, which disclose twoembodiments of the low pressure accumulator 480. Referring to FIG. 34a,low pressure accumulator 480 includes a movable piston 560 slidablypositioned in a cavity 562 extending through spacer housing 478. Sealplugs 564 are threadably secured in each end of cavity 562 on oppositesides of piston 560 to fluidically seal cavity 562. Piston 560 includesa first portion 566 slidably received in one of the seal plugs 564 and asecond portion 568 slidably and sealingly engaging an inner wall ofhousing 478 to divide cavity 562 into a supply section 570 and a drainsection 572. A pressure regulator disc 574 positioned in drain section572 is biased to the left in FIG. 34a against an annular step 575 by ahigh pressure spring 576. A low pressure spring 578, seated at one endagainst pressure regulator disc 574 and at a second end against piston560, biases piston 560 to the left in FIG. 34a. Fuel from gear pump 494(FIG. 30) enters supply section 570 via a supply port (not shown) formedopposite an outlet port 580 connected with the passages 502, 504, 506and 508 supplying fuel to the high pressure fuel pump. Fuel passesthrough passages 582 and 583 extending through first portion 566 to acton both sides of first portion 566 and on one end face of second portion568. As the pressure in cavity 562 increases, the fuel pressure acts onpiston 560 to move piston 560 to the right in FIG. 34a against the forceof low pressure spring 578 to create a reservoir of fuel in cavity 562.As the need for fuel by the high pressure pump exceeds the capacity ofthe gear pump, spring 578 will force piston 560 to the left tosupplement the fuel available from the gear pump. The assemblies ofFIGS. 34a and 34b also function to regulate the pressure within thepressure accumulator cavity 562. As the output of the gear pumpincreases, higher fuel pressure will force piston 560 against pressureregulator disc 574 forcing disc 574 to the right in FIG. 34a against thebias pressure of high pressure spring 576 until a left edge 584 ofsecond portion 568 moves to the right of a land 586 thereby allowingfuel to flow from supply section 570 to drain section 572. Fuel in drainsection 572 is returned to the intake of gear pump 494 via a drain port588 and return passages (not shown). Once the fuel pressure in supplysection 570 decreases to a predetermined level, high pressure spring 576forces piston 560 to the left fluidically sealing supply section 570from drain section 572. In this manner, accumulator 484 maintains asufficient supply of fuel to the pump chambers 482 and 484 of the highpressure pump 486 even during the time of highest retraction velocity ofpump plungers 490 and 492 (FIG. 30).

FIG. 34b illustrates a second embodiment of low pressure accumulator 484having a movable piston 590 positioned in a cavity 592 formed in oneside of spacer housing 478 and fluidically sealed by a seal plug 593.Supply fuel enters and exits the supply section 594 via passages 596 and598. As the pressure in cavity 592 increases, piston 590 is moved to theright in FIG. 34b against the bias pressure of a low pressure spring600. When fuel pressure increases to a predetermined level piston 590contacts pressure regulator disc 602 moving disc 602 to the rightagainst the bias pressure of a high pressure spring 604 thereby allowingsupply fuel to drain through passage 606. As supply fuel pressuredecreases, spring 604 returns disc 602 to its seated position against astep 608.

Referring now to FIG. 35, an alternative hydro-mechanical embodiment ofthe present invention is disclosed which is similar to the previouslydiscussed embodiments in that a high pressure pump unit 700 supplieshigh pressure fuel to an accumulator 702 for sequential delivery to aplurality of injector nozzles, one of which is illustrated at 704, via afuel distributor 706 which includes a rotor 708 which rotates tosequentially deliver fuel from supply ports 710 formed in rotor 708 toreceiving passages 712 formed in a distributor housing 713. However,unlike the previous embodiments, rotor 708 is mounted for axialdisplacement under the influence, at one end, of an engine speed sensingflyweight device 714 and, at the other end, by a spring element 716having a bias force which is adjustable in response to the rotation of acam 718 which may be controlled by throttle position and/or an all speedgovernor. Supply ports 710 include a pilot port 720 which leads thesupply ports 710 to provide a pilot or pre-injection and a generallytriangularly-shaped main injection port 722. The shape of port 722,which registers with receiving passages 712 after further rotation ofrotor 708, is varied in the axial direction of the rotor 708 to causethe amount of fuel injected by the corresponding fuel injector to bevaried in accordance with the axial position of the rotor 708. To varythe timing of each injection event performed by the system, a "phaser"mechanism 724 can be provided to advance or retard rotor 708 relative tothe instantaneous position of the cam shaft. Such a mechanism mayrespond to a mechanical, electrical or fluidic signal to adjust theangular position of rotor 708 relative to the engine cam shaft.

Now referring to FIG. 36, another embodiment of the present invention isillustrated which is similar to the embodiment shown in FIG. 1 exceptthat a rotary pump 750 is used instead of the in-line high pressure pump14 disclosed in FIG. 1. Rotary pump 750 includes pump plungers 752reciprocally mounted in pump chambers 754 formed in a portion of thedrive shaft 756 which constitutes a rotatable pump housing.Alternatively, the pump chambers may be formed in a rotatable pumphousing which is separate from drive shaft 756 but is adapted to rotatewith it. Preferably, drive shaft 756 is also used to drive distributor758 which may be formed in drive shaft 756 or may be formed as aseparate rotatable assembly driven by shaft 756. Distributor 758operates in the same manner as distributor 16 of FIG. 5.

A cam ring 760 through which drive shaft 756 extends includes an innerannular cam surface 762 against which pump plungers 752 are biased by,for example, biasing springs (not shown). In this manner, as drive shaft756 rotates, pump plungers 752 are rotated relative to cam surface 762which alternatively forces plungers 752 inwardly and permits plungers752 to move outwardly as dictated by the contour of cam surface 762.Pump chambers 754 communicate with a common central cavity 764 which iscontinuously connected to pump control valve 766 by, for example, axialpassage 768, radial passage 770, annular groove 772 and connectingpassage 774 formed in a pump housing (not illustrated).

Although not illustrated, the pump housing may be stationary and the camring 760 may be arranged to rotate with drive shaft 756. The radiallyoriented pump chamber may be placed radially inside the cam ring as inFIG. 36 or the pump chambers may be positioned radially outside of thecam surface. Regardless of the cam ring embodiment used, the rotary pumpof FIG. 36 may be integrated in the unitized pump assemblies of thepresent invention as disclosed in FIGS. 5, 28 and 30.

The operation of the embodiment disclosed in FIG. 36 is fundamentallythe same as the embodiment of FIG. 1 except that rotary pump 750operates to move pump plungers 752, in unison, radially inwardly andoutwardly during the rotation of drive shaft 756. When the pump valve766 is open, fuel is allowed to flow from a fuel supply (notillustrated) through pump control valve 766 into pump chambers 754 onthe outward stroke of pump plunger 752. Fuel is forced back out throughpump control valve 766 to the supply upon inward movement of pumpplungers 752 so long as pump control valve 766 is in the open position.When fuel delivery to the accumulator is desired, pump control valve 766is moved to the closed position during the inward stroke of pump plunger752 blocking the flow of fuel to the supply, thus allowing high pressurefuel to the delivered from common central cavity 764 to accumulator 776.This embodiment of the present invention is particularly advantageous inproviding an extremely compact, low cost fuel pumping system readilyadaptable for use with small engines subject to strict size, weight andprice requirements. Moreover, it should be noted that only one pumpcontrol valve is needed for a plurality of pump plungers, therebysimplifying the assembly and the control system.

Referring now to FIGS. 37 and 38, an alternative embodiment of the fueldistributor used in the fuel system of the present invention isdisclosed. Specifically, distributor 780 includes a distributor housing782 containing distributor or injection line valves 784 which areoperated by a rotating camshaft 786 to deliver pressurized fuel throughrespective delivery valves 788 to corresponding engine cylinders (notshown). Distributor housing 782 includes a large cylindrical recess 790in one end of housing 782 for receiving rotating camshaft 786. A seal792 is provided between the outer annular surface of camshaft 786 anddistributor housing 782 to prevent fuel from leaking between camshaft786 and housing 782 while permitting camshaft 786 to rotate. Camshaft786 includes an end face 794 having a cam 796 formed thereon foroperating injection line valves 784 during rotation of camshaft 786. Cam796 is positioned on the outer radial portion of end face 794 forsequentially contacting injection line valves 784.

Distributor housing 782 further includes a plurality of valve cavities798 extending axially along the rotational axis of camshaft 786perpendicular to end face 794. Valve cavities 798 are equally spaced ina circular formation, as shown in FIG. 38, and extend from the inner endof cylindrical recess 790. A supply inlet passage 800 is formed indistributor housing 782 and fluidically connected at one end to theinjection control valve 20 of FIG. 1. The opposite end of supply inletpassage 800 is connected to a common supply chamber 802 which isfluidically connected to each of the valve cavities 798. A respectivefuel injection outlet passage 804 extends radially outward from eachvalve cavity 798 through housing 782 for delivering high pressure fuelto respective fuel injection lines 806 leading to corresponding enginecylinders. The respective spring biased delivery valve 788 is positionedin each fuel injection line 806 to prevent the flow of fuel from eachfuel injection line 806 back through distributor 780.

Injection line valves 784 are each of the spool-type including a slidevalve element 808 positioned for reciprocal movement in a respectivevalve cavity 798. Each slide valve element 808 extends, at one end, intothe inner end of recess 790 adjacent end face 794 of camshaft 786 so asto be positioned for engagement by cam 796 during rotation of camshaft786. The opposite end of each slide valve element 808 extends into itscorresponding valve cavity 798 beyond the connections of fuel injectionoutlet passages 804 and supply chamber 802 to the valve cavity 798. Abias spring 810 is positioned in a cavity 811 formed by the opposite endof slide valve element 808 and a closed end of each valve cavity 798 tobias slide valve element 808 toward camshaft 786 and into abutment withend face 794.

Each slide valve element 808 also includes a cylindrical land 812 sizedto form a close sliding fit with the inside surface of valve cavity 798creating a fluid seal between the adjacent surfaces to prevent fuel fromleaking from outlet passage 804 and supply inlet passage 800 when land812 covers or blocks these passages. Supply valve element 808 alsoincludes an annular groove 814 formed in its outer surface so as to formland 812 on one end of element 808. Annular groove 814 is formed alongvalve element 808 so as to be positioned in communication with commonsupply chamber 802 and fuel injection outlet passage 804 when therespective slide valve element is moved inward by cam 796 against thebias force of spring 810.

Operation of the fuel distributor of FIG. 37 will now be discussed inaccordance with its use in the fuel pump system of the presentinvention. As camshaft 786 rotates, cam 796 sequentially engages slidevalve elements 808 of injection line valves 784 moving a respectiveslide valve element 808 to the right as shown in FIG. 37 against thebias force of spring 810. In this manner, annular groove 814 moves intocommunication with common supply chamber 802 and fuel injection outletpassage 804, placing injection line valve 784 in an open positionfluidically connecting supply inlet passage 800 with a respectiveinjection line 806. As camshaft 786 continues to rotate, cam 796 passesby the end of slide valve element 808 allowing slide valve element 808to return to a closed position under the force of bias spring 810,wherein land 812 blocks the flow between common supply chamber 802 andfuel injection outlet passage 804. The opening and closing of eachinjection line valve 784 defines a respective potential injection periodor window of opportunity during which injection may occur as determinedby the operation of injection control valve 20 shown in FIG. 1. However,at any given time during the rotation of camshaft 786, only oneinjection line valve 784 is in an open position defining the injectionperiod. Injection control valve 20 opens and subsequently closes duringeach injection period to define an injection event during which highpressure fuel from high pressure accumulator 12 is delivered via supplyinlet passage 800, common supply chamber 802 through a respectiveinjection line valve 784 into outlet passage 804 and a respectiveinjection line 806 for delivery to a respective injector nozzle assembly11 and associated engine cylinder (not shown). Injection line valve 784also includes an equalizing passage 816 extending from one end of slidevalve element 808 to the opposite end so as to communicate recess 790with spring cavity 811. In this manner, any pressure developing inrecess 790 and spring cavity 811 due to fuel leaking between slide valveelement 808 and distributor housing 782 can be equalized to permitmovement of slide valve element 808. Also, although not shown, a drainpassage may be used to connect spring cavity 811 and/or recess 790 to alow pressure fuel drain. Alternatively, spring cavity 811 and recess 790may be filled with lube oil via a passage (not shown) communicating withrecess 790. In addition, other forms of distributors may be used in thepresent fuel system including the distributors discloses in commonlyassigned U.S. patent application Ser. No. 117,697 entitled Distributorfor High Pressure Fuel Injection System which is hereby incorporated byreference.

FIGS. 39 and 40 represent two further embodiments of the high pressurepump assembly of the present invention as shown in FIG. 6. Components ofthese embodiments which are the same as components disclosed in FIG. 6will be referred to with like reference numerals. Both the embodimentsof FIGS. 39 and 40 advantageously reduce the number of components of theassembly and the complexity of the manufacturing process, therebyadvantageously reducing the costs of the entire system. Moreover, theseembodiments reduce the potential for fuel leakage from the pump chamberby reducing the number of sealed joints subject to high fuel pressure.

As shown in FIGS. 39 and 40, these embodiments achieve the above-notedadvantages by avoiding the use of sealing disk 112 of the embodimentshown in FIG. 6. The embodiment of FIG. 39 includes a one-piece pumpbarrel 820 having an inner end 822 positioned in compressive abutmentwith accumulator housing or pump head 34 under the force of retainer104. The pump unit check valve 824 extends into a pump outlet passage826 extending through inner end 822 along the central axis of the pumpchamber 828. Pump unit check valve 824 is adapted to sealingly engage acheck valve seat 829 formed on the upper annular surface of pump barrel820 surrounding pump outlet passage 826 to prevent the flow of highpressure fuel from accumulator chamber 36c when the pressure of the fuelin chamber 36c is greater than the pressure of the fuel in pump chamber828 while permitting fuel from chamber 828 into accumulator chamber 36cwhen the pressure in pump chamber 828 exceeds the fuel pressure inaccumulator chamber 36c. Check valve 824 is biased into the closedposition against check valve seat 829 by a bias spring 830 positioned ina delivery passage 832. A spring guide pin 834 extends from accumulatorchamber 36c into delivery passage 832 for guiding spring 830 whileproviding a seating surface for spring 830. Pump barrel 820 alsoincludes a pair of pump inlet passages 836 extending from pump chamber828 to connect with an annular groove 838 formed in the top surface ofpump barrel 820. As described more fully hereinabove with respect toFIG. 6, annular groove 838 is fluidically connected to pump controlvalve 18, 19 by a respective fuel passage 840 and fuel feed branchpassage 842. The operation of this embodiment is substantially the sameas that described in relation to FIG. 6 hereinabove.

Referring now to FIG. 40, another embodiment of the pump assemblyincludes a pump barrel 844 positioned in abutment with pump head 34 soas to position pumping chamber 846 immediately adjacent pump head 34.Pump head 34 extends across pump chamber 846 to form at least a partialend wall 848 of pump chamber 846. In this embodiment, no pump inlet andoutlet passages are formed in pump barrel 844 since pump inlet andoutlet passages 850 and 852 respectively are formed completely in pumphead 34. A check valve 854 is positioned in outlet passage 852 forabutment against a check valve seat 856 formed annularly around outletpassage 852. A check valve assembly cavity 858 extends from the uppersurface of pump head 34 downwardly to communicate with pump outletpassage 852 to permit easy installation of check valve 854 and itsassociated spring 860 and guide pin 862. A sealing plug 864 isthreadably engaged in check valve assembly cavity 858 to seal cavity 858while providing support for spring 860 and guide pin 862. Both theembodiments shown in FIGS. 39 and 40 advantageously create only one highpressure joint between the inner end of each pump barrel and theabutting pump head. This design minimizes the amount of fuel leakage andreduces the time and expense involved in forming metal to metal sealingsurfaces, thereby ensuring effective high pressure operation of the pumpat reduced cost.

Reference is now made to FIGS. 41 through 43 which disclose yet anotherembodiment of the subject invention. This embodiment is substantiallythe same as the embodiment shown in FIG. 30 discussed hereinabove withregards to the single solenoid operated three-way injection controlvalve 454, the distributor 464, gear pump 494 and the lower portion ofhigh pressure pump assembly 486. However, in this embodiment, anaccumulator housing or pump head 870 is integrated with the upperportion of high pressure pump assembly 486 so as to minimize the overallheight of the fuel pump assembly. In particular, pump chambers 872 and874 are formed directly in the accumulator housing 870. The pumpchambers 872 and 874 are formed along a respective radial pump axisextending through outwardly opening pump cavities 876, 878 housing pumpunits 880 and 882. Pump plungers 884, 886 extend into the respectivepump chambers 872 and 874 for reciprocal movement during the rotation ofthe drive shaft 888. Pump chambers 872 and 874 are formed by respectivepump barrels 890 and 892 formed integrally with accumulator housing/pumphead 870. Pump barrels 890 and 892, formed integrally with accumulatorhousing 870, each extend inwardly into respective pump cavities 876, 878to support pump plungers 884, 886. Respective annular spring recesses894 and 896 are formed around respective pump barrels 890, 892 forreceiving and supporting one end of respective bias springs 898 and 900.Accumulator housing/pump head 870 also includes a pair of pump valverecesses 902 and 904 formed in a sidewall 906 and extending transverselyinto the housing for receiving pump control valves 18, 19. A respectivecavity 908, 910 extends laterally through housing 870 from each pumpvalve recess 902, 904 respectively, to an opposite side wall 912 forreceiving a respective control valve element 914 (FIG. 43) of arespective pump control valve 18, 19. Each valve cavity 908, 910 ispositioned axially along housing 870 directly above respective pumpchambers 872, 874 so that pump chambers 872, 874 open directly intorespective valve cavities 908, 910.

As shown in FIGS. 41 and 42, annular grooves 916, 918 are formed inrespective valve cavities 908, 910 transversely between respective pumpchambers 872, 874 and side wall 912. A common axial transfer passage 920extends axially through housing 870 so as to connect annular grooves 916and 918. Common axial transfer passage 920 extends from valve cavity 910axially to intersect a cross passage 922 extending transversely througha portion of accumulator housing 870 from side wall 912. The open endsof transfer passage 920 and cross passage 922 are fluidically sealed byplugs 920 a and 922 a positioned in a recess formed in the open end.Accumulator housing 870 also includes two accumulator chambers 924 and926 extending axially into the housing from an end wall 928. Arespective axial passage 930, 932 connects each accumulator chamber 924,926 to cross passage 922. As shown in FIG. 43, accumulator housing 870also includes a respective supply passage 934 associated with each pumpcontrol valve 18, 19. Generally, pump control valves 18 and 19 are eachpreferably a solenoid-operated valve assembly similar to the typedisclosed in commonly assigned U.S. Pat. No. 4,905,960 to Barnhart. Themounting arrangement of pump control valves 18 and 19 in pump head 870is structurally the same. Only the differences in pump control valve 18will be described hereinbelow. In this particular application, pumpcontrol valve 18 includes a spring housing 936 positioned between asolenoid casing 938 and a valve seat member 940. Valve seat member 940is positioned in a compressive fluid sealing abutting relationshipbetween spring housing 936 and an annular abutment surface 942 formed onaccumulator housing 870 around valve cavity 908. Valve seat member 940extends radially inward around valve cavity 908 to form an annular valveseat 944. Pump control valve 18 also includes a valve member 946reciprocally mounted in valve cavity 908 for controlling the flow offuel to and from pumping chamber 872. Valve member 946 includes anannular conical surface 948 for engaging valve seat 944 when valvemember 946 is moved into a closed position. An armature 950 is connectedto one end of valve member 946 adjacent solenoid coil assembly 952 to bepulled toward the solenoid coil assembly 952 when the coil assembly isenergized. A valve biasing spring 954 is positioned in an annular cavity956 formed in spring housing 936 for biasing conical surface 948 ofvalve member 946 away from valve seat 944 into an open position. Springhousing 936 is positioned relative to the inner surface of pump valverecess 902 to form an annular gap 958 in communication with supplypassage 934. Valve seat member 940 includes radial passages 960 incommunication with annular gap 958. Valve member 946 is positionedrelative to valve seat member 940 to form a first annular passage 962 incommunication with radial passages 960 on one side of valve seat 944. Onthe opposite side of valve seat 944, valve member 946 is positionedrelative to the inner annular surface of valve cavity 908 to form asecond annular passage 964 which communicates at one end with firstannular passage 962 when valve member 946 is in the open position, andwith pumping chamber 872 at an opposite end.

As shown in FIG. 43, valve member 946 of pump control valve 18 alsoincludes a pump outlet passage 966 connecting pumping chamber 872 with acheck valve cavity 968 formed centrally in valve member 946. A springbiased check valve 970 is positioned in check valve cavity 968 andbiased by a check valve spring 972 against a check valve seat 974 formedon the inner annular surface of valve member 946 in cavity 968. A springguide pin 976 is also positioned in check valve cavity 968 and securedto valve member 946 by an inner snap ring 978. Therefore, the checkvalve assembly including check valve 970, check valve spring 972 andspring guide pin 976 reciprocate with valve member 946 during operationof pump control valve 18. The open end of each valve cavity 908, 910 isfluidically sealed by a plug 980 threaded into a recess formed in theopen end. A valve stop 982 is threadedly engaged with the plug 980 toform an abutment for the outer annular end of valve member 946 whenvalve member 946 is moved into the open position by biasing spring 954.Valve stop 982 includes an inner extension 983 for abutment by guide pin976. By rotating valve stop 982 relative to plug 980, the transverseposition of valve stop 982 relative to valve member 946 and, thus, thevalve stroke of valve member 946 may be adjusted.

Valve member 946 further includes radial passages 984 arranged to allowfluid communication between check valve cavity 968 and annular groove916. Check valve seat 974 is positioned along check valve cavity 968between pump outlet passage 966 and radial passage 984 to allow checkvalve 970 to prevent the back flow of high pressure fuel fromaccumulator chambers 924, 926 when in the closed position whilepermitting high pressure fuel from pumping chambers 872, 874 to flow tothe accumulator chambers 924, 926 when valve member 946 moves to theclosed position. Accumulator housing 870 also includes a drain passage986 extending from valve cavity 908 adjacent valve stop 982 to a lowpressure drain (not shown).

The pump assembly of FIGS. 41-43 is particularly advantageous in severalrespects. First, by forming the pump barrels 890, 892 integral withpumphead/accumulator housing 870 and mounting the pump control valves18, 19 in the side of the accumulator so as to extend transverselythrough the accumulator housing 870. The accumulator housing 870 can bemoved closer to the drive shaft 888 resulting in a more integrated,compact and lightweight pump assembly. As shown in FIG. 41, this compactassembly permits contiguous positioning of injection control valve 454between an axial overhang 987 of accumulator housing 870 and distributor464. Instead of a vertical feed tube connecting the accumulator to theinjection control valve as shown in the previous embodiments, a feedtube 989 is connected at one end to a plug 991 positioned in the openend of accumulator chamber 926 and loops around to connect with the sidewall of the housing containing injection control valve 454. Secondly,this integrated assembly reduces the volume of high pressure fueltrapped in the high pressure passages during a pump delivery strokesince the pumping chambers are moved immediately adjacent the valvecavities and valve seats. This reduction in trapped volume translatesinto increased pumping efficiency for each stroke of the high pressurepump since a greater portion of the total volume of fuel subjected tovery high pressure is actually transferred into the accumulator. As aresult, the horsepower of the engine may be increased for a given sizefuel pump assembly since less power is consumed by the high pressurepump in pumping the same amount of fuel into the accumulator as comparedto a similar system without this feature. Third, because the pumpchamber is moved into the accumulator housing, this design minimizes thenumber of high pressure joints between the pump chamber and theaccumulator chambers.

Referring now to FIGS. 44 and 45, another embodiment of the presentinvention is illustrated. Generally, this embodiment discloses a novelpump assembly including a pump head 990, a pair of pump units 992 and993, and corresponding pressure balanced pump control valves 994 and997. The pump units 992 and 993, and associated pump control valves 994and 997 are structurally the same and, therefore, only pump unit 992 andpump control valve 994 will be discussed hereinbelow. Although notshown, fuel pump assembly 988 may be used with, or mounted on, the samecomponents of the fuel pumping systems disclosed in FIGS. 5, 28 and 30,including the solenoid operated three-way injection control valve(s),the distributor, and the lower portion of the high pressure pumpassembly. As shown in FIG. 44, pump unit 992 includes a pump barrel 995held in a pump recess 996 by a pump retainer 998 having external threadsfor engaging complementary threads formed on the inner annular surfaceof a counter bore 1000 formed in the outer end of recess 996. Pump unit992 also includes a pump chamber 1002 formed in barrel 995 and a pumpplunger 1004 positioned for reciprocal movement within pump chamber 1002in response to the rotation of the drive shaft (not shown). Pump barrel995 includes an inner end 1006 positioned in abutment with the pump head990. A pump unit outlet passage 1008 extends through inner end 1006 frompump chamber 1002. A discharge passage 1010 is formed in pump head 990to connect outlet passage 1008 to an accumulator chamber 1012. A pumpunit check valve assembly 1014 is positioned in accumulator chamber1012, discharge passage 1010 and pump unit outlet passage 1008. Checkvalve assembly 1014 includes a check valve element 1016, biasing spring1018 and guide pin 1020. Check valve element 1016 is biased by spring1018 into abutment with an annular valve seat 1022 formed on pump barrel995 around outlet passage 1008 so as to prevent fuel flow fromaccumulator chamber 1012 into pump chamber 1002 while permitting fuelflow from pump chamber 1002 into accumulator chamber 1012 when the fuelpressure in chamber 1002 is greater than the fuel pressure in chamber1012. A facer plate 1024 and sealing ring 1026 are positioned aroundannular seat 1022 between pump barrel 995 and pump head 990 to preventhigh pressure fuel from leaking between these components. Alternatively,facer plate 1024 and sealing ring 1026 may be omitted to form a metal tometal joint between pump barrel 995 and pump head 990. An outer annulargroove 1028 is formed between the pump barrel 995 and pump head 990 toreceive any high pressure fuel that leaks through the sealed connectionprovided by either facer plate 1024 and sealing ring 1026 or a metal tometal interface. A drain connector passage 1030 extends from annulargroove 1028 to connect with a combined drain passage 1032 for directingleak-by fuel from annular groove 1028 to drain via a main drain passage1034 formed in the pump housing. A similar drain connector passage (notshown) associated with pump unit 993 connects to main passage 1034.

A lubrication flow passage 1036 extends through pump barrel 995 fromannular groove 1028 to connect with an annular lubrication channel 1038formed in barrel 995 around chamber 1002. First and second annularlubrication grooves 1040 and 1042, respectively, are formed in plunger1004 and connected by cross passage 1044. During the reciprocal movementof plunger 1004 in chamber 1002, first and second annular lubricationgrooves 1040, 1042 are intermittently connected to annular lubricationchannel 1038. In this manner, low pressure fuel from annular groove 1028is used to lubricate plunger 1004 thereby minimizing friction betweenplunger 1004 and the inner surface of pump barrel 995 thus minimizingwear, scuffing and scoring of the contacting surfaces.

A valve cavity 1046 extends diametrically through pump barrel 995 so asto intersect the inner end of pumping chamber 1002 and the outer end ofoutlet passage 1008. Valve cavity 1046 also extends through pump head990 to connect with a plug recess 1048 at one end and a spring chamber1050 at the opposite end. The open end of valve cavity 1046 adjacentrecess 1048 is fluidically sealed by a plug 1052 threadably engagingpump head 990 in recess 1048. Pressure balanced pump control valve 994includes a valve operator 1054 mounted on one side of pump head 990 anda control valve element 1056 mounted for reciprocal movement in valvecavity 1046. Control valve element 1056 includes an annular valvesurface 1058 for abutment against an annular valve seat 1060 formed onpump barrel 995 around valve cavity 1046 when pressure balanced pumpcontrol valve 994 is in a closed position. A biasing spring 1059 ispositioned in spring chamber 1050 for biasing control valve element 1056into an open position. Fuel is delivered to pump chamber 1002 via a mainsupply passage 1062 formed in the pump housing, a connector passage 1064formed in a lower portion of pump head 990 and a cross feed passage 1066which extends longitudinally through pump head 990 to fluidicallyconnect spring chamber 1050 of one pump control valve 994 to an adjacentpump control valve as shown in FIG. 45. An annular channel 1067 isformed in pump head 990 around pump recess 996 adjacent valve cavity1046. An annular gap 1068 formed between control valve element 1056 andthe inner surface of valve cavity 1046 connects spring chamber 1050 toannular channel 1067. On the opposite end of valve cavity 1046, annularchannel 1067 is connected to chamber 1002 by an annular gap 1070 formedbetween control valve element 1056 and the inner surface of valve cavity1046. Annular valve seat 1060 is formed along annular gap 1070 betweenannular channel 1067 and chamber 1002. In this manner, annular valvesurface 1058 can be moved into and out of engagement with annular valveseat 1060 to control the flow of fuel into and out of pump chamber 1002.

Pressure balanced pump control valve 994 may be any conventionalsolenoid operated, pressure balanced two-way valve adaptable for use inthis design. The control valve element 1056 of pressure balanced pumpcontrol valve 994 is pressure balanced in the closed position becausethe fluid pressure forces resulting from high pressure fluid acting oncontrol valve element 1056 in one direction, i.e., to the right in FIG.44, equal the fluid pressure forces resulting from high pressure fluidacting on control valve element 1056 in the opposite direction, i.e., tothe left in FIG. 44, since the effective cross sectional area of valveseat 1060 which remains exposed to the fluid pressure found in the pumpchamber is equal to the effective cross-sectional area defined in theportion of valve element 1056 received in the pump barrel on the rightside of pump chamber 1002, control valve element 1056 causing therightward forces equals the surface area of the control valve element1056 causing the leftward forces.

During operation, fuel is delivered by a supply pump (not shown) throughmain supply passage 1062, connector passage 1064 and cross feed passage1066 into spring chamber 1050. Fuel flows from spring chamber 1050through annular gap 1068 surrounding control valve element 1056, annularchannel 1067 surrounding barrel 995 into annular gap 1070 adjacentannular valve seat 1060. When pressure balanced pump control valve 994is in the de-energized open position, fuel flows between annular valveseat 1060 and annular valve surface 1058 into pump chamber 1002. As pumpplunger 1004 reciprocates, fuel flows into, and is pumped out of, pumpchamber 1002 via these supply passages. Upon the need for fuel deliveryto accumulator chamber 1012, valve operator 1054 of pump control valve994 will be energized during the advancing movement of the pump plunger1004 to move control valve element 1056 to the right in FIG. 44, thuscausing annular valve surface 1058 to engage annular valve seat 1060. Asa result, fuel flow through annular gap 1070 is blocked allowing pumpplunger 1004 to compress and pressurize any fuel remaining in pumpchamber 1002. Upon reaching a pressure level greater than the fuelpressure level in accumulator chamber 1012, fuel in pump chamber 1002will open check valve element 1016 and flow through outlet passage 1008and discharge passage 1010 into accumulator chamber 1012. Depending onthe control scheme used, at some point in time during the advancing orretracting movement of pump plunger 1004, pressure balance pump controlvalve 994 will be de-energized to permit check valve element 1016 tomove into an open position under the force of biasing spring 1059. Theadvantage of using a pressure balanced valve is that greater latitudeexists for opening and closing the pump control valve. In particular, itbecomes readily possible to terminate the effective pumping stroke ofpump plunger 1004 during any point in the advancing stroke withoutresulting in very high spring or solenoid forces that would be requiredif an unbalanced valve structure were used.

Reference is now made to FIG. 46 disclosing another embodiment of thepresent invention which is the same as the embodiment of FIGS. 44 and 45except that a pump head 1072 does not include any accumulator chambersfor accumulating a quantity of fuel. As will be explained more fullyhereinbelow in relation to the embodiment of FIGS. 52 and 53, pump head1072 merely includes a single common transfer passage 1074 for receivingfuel from the one or more pumping chambers 1002. One end of commontransfer passage 1074 is connected to an off-mounted accumulatorpositioned a spaced distance from the fuel pump assembly as shown inFIG. 52. This arrangement results in a more compact fuel pump assemblywhile permitting mounting of the high pressure accumulator in a moreappropriate and advantageous location on the engine.

FIG. 47 represents yet another embodiment of the fuel pump assembly ofthe present invention which is the same as the embodiments disclosed inFIGS. 5, 28 and 30 except that a pressure balanced pump control valve1076 is used. Pressure balanced pump control valve 1076 may be anyconventional two-way pressure balanced solenoid-operated valve. A pumpcontrol valve cavity 1080 extends upwardly from a valve recess 1082formed in a lower surface of accumulator housing 1078. Valve cavity 1080opens into a plug recess 1084 which is fluidically sealed by a plug1086. Plug 1086 terminates prior to the end wall of recess 1084 to forma chamber 1088. Pump control valve 1076 includes a control valve element1090 which extends through valve cavity 1080 and terminates at one endin chamber 1088. An annular valve seat 1092 formed around valve cavity1080 adjacent chamber 1088 is positioned for abutment by an annularvalve surface 1094 formed on control valve element 1090. An annularrecess 1096 may be formed in valve cavity 1080 adjacent control valveelement 1090 between valve seat 1092 and valve recess 1082. An annularchannel 1098 formed between control valve element 1090 and the innerwall of valve cavity 1080 fluidically connects chamber 1088 to annularrecess 1096 when control valve 1076 is in the open position.

The fuel feed passages formed in accumulator housing 1078 aresubstantially the same as those disclosed in FIGS. 5-10L, with theexception of the following modifications. First, connector passages 92and 94 shown in FIG. 1Oe which supply fuel from common fuel feed passage90 to both pump control valves, would extend from each chamber 1088downwardly to communicate with passage 90 instead of extending upwardlyfrom pump control valve recess 1082 as suggested by the embodiment ofFIGS. 5 and 10e. Also, accumulator chamber 36a will necessarily beshorter in length so as to terminate prior to plug recess 1084.Operation of the embodiment of FIG. 47 is substantially the same as thatof the embodiment shown in FIG. 6 except that pump control valve 1076 ispressure balanced when in the closed position blocking fuel flow betweenthe fuel supply and the pump chamber thus permitting the control schemeflexibility discussed with respect to the embodiment disclosed in FIGS.44-45.

Referring now to FIGS. 48-51, another embodiment of the presentinvention is disclosed. Referring to FIG. 48, pump control valves 1100and 1102 are vertically mounted in respective valve recesses 1104 and1106 formed in the top surface 1108 of accumulator housing 1110. Pumpcontrol valves 1100 and 1102 are each preferably a solenoid-operatedvalve assembly of the type disclosed in commonly assigned U.S. Pat. No.4,905,960 to Barnhart. Pump units 1112 and 1114 are mounted incorresponding pump unit recesses 1116 and 1118 formed in the lowersurface of accumulator housing 1110 directly below corresponding valverecesses 1104 and 1106. The formation of the fuel passages inaccumulator housing 1110 associated with each pump control valve 1100and 1102 are structurally the same and, therefore, only one set ofpassages and components will be described herein below.

Referring to FIG. 49, a pump outlet passage 1120 extends from valverecess 1104 to the pumping chamber of pump unit 1112 to form a valvecavity for receiving a valve element 1122 of pump control valve 1100. Adischarge passage 1124 extends from one side of accumulator housing 1110transversely inwardly to connect with pump outlet passage 1120. The openend of discharge passage 1124 is fluidically sealed with a plug 1126. Apump unit check valve 1128 is positioned in discharge passage 1124 andadapted to sealingly engage an annular valve seat surrounding dischargepassage 1124. A vertical passage 1132 extends upwardly from the lowersurface of accumulator housing 1110 through discharge passage 1124 toconnect with an accumulator chamber 1134d formed in accumulator housing1110. A similar vertical passage 1133 associated with pump unit 1114connects a respective discharge passage (not shown) with accumulatorchamber 1134d. A main supply passage 1136 formed in pump housing 1138supplies low pressure fuel to pump control valve 1100 via a connectorpassage 1140 and a branch passage 1142. A similar branch passage 1143extends from connector passage 1142 to supply fuel to the other pumpcontrol valve 1102. It should be noted that although pump units 1112 and1114 are illustrated as being similar to the embodiment disclosed inFIG. 40 and described hereinabove, the pump units may take the form of adifferent embodiment.

Referring now to FIGS. 50 and 51, the accumulator housing 1110 of theembodiment illustrated in FIGS. 48-49 includes an upper row of elongatedaccumulator chambers 1134a-d (FIG. 50) and a lower row of elongatedaccumulator chambers 1134e-g. Each of the accumulator chambers areformed by drilling longitudinally through accumulator housing 1110 froman end wall 1144. The open end of each accumulator chamber isfluidically sealed with the respective plug 1146. The upper row ofaccumulator chambers are connected by a first cross passage 1148extending transversely from one side of accumulator housing 1110 througheach of the accumulator chambers 1134a-d. Accumulator housing 1110further includes a pair of recess drain passages 1150 and 1152 extendingfrom respective pump unit recesses 1116 and 1118 for directing fuelleakage collecting in respective recess clearances 1154 and 1156 to amain drain passage 1158. As shown in FIG. 50, accumulator chamber 1134cterminates about midway through accumulator housing 1110 adjacent firstcross passage 1148. Accumulator chambers 1134e-g are also interconnectedby a second cross passage 1160 (FIG. 51) extending transversely throughaccumulator housing 1110 in the same vertical plane as the first crosspassage 1148. The upper and lower rows of accumulator chambers areconnected by a vertical passage 1162 extending upwardly from secondcross passage 1160 to connect with accumulator chamber 1134c. A fuelfeed passage 1164 extending from the lower surface of accumulatorhousing 1110 also communicates with accumulator chamber 1134c. A recess1166 formed in the open end of fuel feed passage 1164 is adapted toreceive a fuel feed tube 1169 (FIG. 48) for supplying the temporarilystored fuel in the accumulator chambers to the fuel injection controlvalve(s) (not shown) for delivery to the engine via a distributor (notshown) as described hereinabove in relation to various otherembodiments.

Referring now to FIGS. 52 and 53a, another embodiment of the presentinvention is shown which is the same as the previous embodiment of FIGS.48 and 49 except that an accumulator 1168 is positioned a spaceddistance from a pump head 1170. Pump head 1170 does not include anyaccumulator chambers but merely one elongated common transfer passage1172 connected to vertical passages 1132, 1133 for receiving highpressure fluid from each pump unit 1112, 1114. The accumulator 1168includes an accumulator housing 1174 forming a generally cylindricalaccumulator chamber 1176. However, accumulator 1168 may include multipleinterconnected accumulator chambers similar to the embodiments of FIGS.7 and 50. One end of accumulator chamber 1176 is fluidically sealed witha plug having a stepped recess 1180 for receiving a pressure sensor1182. A center passage 1184 connects stepped recess 1180 to accumulatorchamber 1176 thereby permitting pressure sensor 1182 to monitor the fuelpressure in accumulator chamber 1176. The opposite end of accumulatorchamber 1176 is fluidically sealed with an adapter 1186 having an innerrecess 1188. Adapter 1186 also includes an inlet passage 1190 and anoutlet passage 1192 extending from the inner end of inner recess 1188. Afuel transfer tube 1194 is connected at one end to common transferpassage 1172 and at an opposite end to inlet passage 1190 for deliveringfuel from common transfer passage 1172 to accumulator chamber 1176. Afuel feed tube 1196 is connected at one end to outlet passage 1192 fordelivering high pressure fuel from accumulator chamber 1176 to theinjection control valve (not shown). The open ends of common transferpassage 1172, inlet passage 1190 and outlet passage 1192 includerespective recesses 1198 having a tube seat 1200 for engaging a tubehead 1202 formed on the end of the respective tube 1194, 1196. Eachrecess 1198 includes internal threads for engaging complementaryexternal threads formed on a generally cylindrical tube fitting 1204.Each tube 1194, 1196 extends through the respective tube fitting 1204 sothat one end of tube fitting 1204 abuts tube head 1202. Rotation of tubefitting 1204 relative to recess 1198 and the respective tube 1194, 1196forces tube head 1202 inwardly into sealing engagement with tube seat1200 thereby creating a fluidically sealed connection between therespective passage 1172, 1190, 1192 and the respective tube 1194, 1196.

The off-mounted accumulator design of FIGS. 52 and 53a permits theaccumulator 1168 to be mounted in possibly more appropriate/advantageouslocations around the engine. Moreover, the pump head 1170 is reduced insize in both the axial direction as shown in FIG. 52 and in thetransverse direction as shown in FIG. 53a. This reduction in pump headsize creates a more compact assembly which may more appropriately fitwithin the packaging constraints of certain engine or vehicle designs.

Reference is now made to FIG. 53b disclosing yet another embodiment ofthe present invention which is the same as the previous embodiment ofFIGS. 52 and 53a and, therefore, like components will be referenced towith the same reference numerals. In this embodiment, a separatelyformed accumulator housing 1187 is connected to a pump head 1189.Accumulator housing 1187 is generally cylindrical in shape and includesan accumulator chamber 1191 having a closed end 1193 and an open end1195. Open end 1195 is threadably secured in a recess 1197 formed in anend wall 1199 of pump head 1189 to form a fluidically sealed connectionbetween accumulator housing 1187 and pump head 1189. Common transferpassage 1172 extends through pump head 1189 to connect with recess 1197and accumulator chamber 1191 for delivering high pressure fuel from pumpunits 1112, 1114 to chamber 1191. Pressure sensor 1182 is positioned ina recess 1201 formed in closed end 1193 and connected to accumulatorchamber 1191 by a passage 1203. The assembly of FIG. 53b is especiallyadvantageous in providing a compact, unitized high pressure fuel pumpassembly having an accumulator which is inexpensive to manufacture andeasily mountable on the assembly.

Reference is now made to FIGS. 54a and 54b which disclose edge filterassemblies used to capture small foreign particles in the fuel flowingfrom the accumulator to the injection control valve (not shown). It isknown that the intermeshing gears of a gear pump, such as boost pumps406 and 494 shown in FIGS. 28 and 30 respectively, often contact eachother as they mesh during normal operation to form small metalparticles. If not captured by the boost pump's filter, these metalparticles will be carried by the fuel through the fuel pumping system.However, it has been found that these particles interfere with thesuccessful operation of the injection control valve and distributor ofthe present invention. Both the injection control valve and distributorrely on extremely small clearances between components thereof to allowone or more of the components to move relative to the other whilecreating a fluidic seal at the clearance. Foreign particles in the fuelbecome lodged between the components in these clearances resulting inexcessive wear or even binding of the moving part and possibly thegradual loss of the fluidic seal. As a result, it is desirable toposition a filter in the fuel path upstream of the injection controlvalve which is capable of removing small particles from the fuel.

FIG. 54a discloses an edge filter assembly 1206 positioned along thefuel flow path between the accumulator 1208 and the injection controlvalve (not shown). Edge filter assembly 1206 includes an edge filter1210 positioned in a filter cavity 1212 formed in one end of a fuel feedtube 1214 of a feed tube attachment assembly 1216. Tube attachmentassembly 1216 is the same as the tube fitting connections describedhereinabove in relation to the embodiments shown in FIGS. 5 and 52except that the end of feed tube 1214 includes the filter cavity 1212sized to house edge filter 1210. As shown in FIG. 54b, the edge filtermay also be positioned in a filter housing 1218 positioned along a fuelfeed tube 1220. In this instance, conventional high pressure tubeattachment assemblies 1222 are used to attach each end of feed tube 1220to a respective end of filter housing 1218. In both the embodiments ofFIGS. 54a and 54b, edge filter 1210 functions to advantageously preventsmall particles from flowing through the fuel system downstream ofaccumulator 1208 thereby preventing foreign particle induced wear and/ordamage to the injection control valve and distributor.

Reference is now made to FIGS. 55a-55c disclosing various otherembodiments of the accumulator of the present invention. Theaccumulators discussed hereinabove with respect to the previousembodiments of the present invention have all included an accumulatorhousing having an accumulator chamber with an open end fluidicallysealed by a plug having external threads for engaging complementaryinternal threads formed on the inner surface of a recess formed in theopen end of one or more chambers. Although such threaded connectionsalso include some type of seal, such as an O-ring, at extremely highfuel pressures, such sealed threaded connections may develop a leakpermitting fuel to drain from the accumulator chamber causing anundesirable loss of fuel pressure in the accumulator, thus adverselyaffecting the metering of fuel.

FIGS. 55a-55c disclose alternative embodiments of the accumulator whichprevent fuel leakage from the ends of the accumulator chambers. FIG. 55adiscloses an accumulator housing 1230 which includes a stepped recess1232 formed in one end of housing 1230. Accumulator chambers 1234 areformed by drilling through an inner end wall 1236 of stepped recess1232. An end plate 1238 is then positioned in stepped recess 1232against a step 1233 formed by stepped recess 1232. End plate 1238 maythen be securely and sealingly connected to accumulator housing 1230 bywelding along a peripheral joint 1240 formed between the outerperipheral edge of end plate 1238 and the edge of accumulator housing1230 defining the open end of stepped recess 1232. A common flow cavityis formed between the inner end wall 1236 and the inner surface of endplate 1238 for permitting the flow of fuel between accumulator chambers1234. The welded peripheral joint 1240 is extremely effective in sealingaccumulator chambers 1234. Consequently, this embodiment results in anaccumulator housing 1230 having a single welded end plate 1238 which ishighly resistant to fuel leakage.

FIG. 55b discloses another embodiment of the accumulator of the presentinvention which is the same as the embodiment disclosed in FIG. 55aexcept that a second stepped recess 1242 is formed at the opposite endof accumulator housing 1230 for receiving a second end plate 1243.

FIG. 55c discloses a third embodiment of the accumulator of the presentinvention which includes an accumulator housing 1244 formed by thewelded connection of a first accumulator block 1246 and a secondaccumulator block 1248. The accumulator chambers and any otherlongitudinal passages are formed in each block 1246, 1248 fromrespective end walls 1250, 1252 prior to joining the blocks 1246, 1248.End walls 1250, 1252 are then positioned in abutment to form aperipheral joint 1254 extending around the entire accumulator housing.The peripheral joint is then welded to securely attach blocks 1246 and1248 while creating a seal for preventing fuel leakage from theaccumulator chambers (not shown). The accumulator embodiments disclosedin FIGS. 55a-55c substantially reduce the likelihood of fuel leakagefrom those areas of the accumulator housing used to form the accumulatorchambers.

Reference is now made to FIGS. 56-62 which disclose several deviceswhich may be incorporated into the fuel system of the present inventionto provide rate shaping capability. By reducing the rate at which fuelpressure increases at the nozzle assembly during the initial phase ofinjection and, therefore, reducing the initial fuel quantity injectedinto the combustion chamber, the various embodiments of the presentinvention are better able to achieve various objectives such as moreefficient and complete fuel combustion with reduced emissions. The rateshaping devices discussed hereafter are designed to better enable thesubject fuel system to meet the ever increasing requirements fordecreasing emissions.

Referring initially to the embodiment shown in FIG. 56, a rate shapingdevice indicated generally at 1260 is positioned along the fuel transfercircuit 1262 between the fuel injection control valve 20 and thedistributor 16 of FIG. 1. However, rate shaping device 1260 could beutilized in any of the embodiments of the present fuel delivery systemdisclosed hereinabove. Also, for purposes of illustration, rate shapingdevice 1260 is shown in FIG. 56 positioned in a distributor housing1264. However, device 1260 may be integrated into fuel transfer circuit1262 anywhere between injection control valve 20 and distributor 16.

As shown in FIG. 56, rate shaping device 1260 includes a flow limitingvalve 1266 positioned within fuel transfer circuit 1262 and a rateshaping by-pass valve 1268 positioned in a by-pass passage 1270. Flowlimiting valve 1266 includes a slidable piston 1272 mounted for slidingmovement within a piston chamber 1274 formed in fuel transfer circuit1262 so as to create a fuel inlet 1276 and a fuel outlet 1278. Slidablepiston 1272 includes a first end 1280 positioned adjacent fuel inlet1276, a second end 1282 positioned adjacent fuel outlet 1278 and acentral bore 1284 extending from first end 1280 inwardly to terminate atan inner end 1286. Slidable piston 1272 also includes an outercylindrical surface 1288 which may have a sufficiently close sliding fitwith the inside surface of piston chamber 1274 to form a fluid sealbetween surface 1288 and the inside surface of piston chamber 1274.Second end 1282 of slidable piston 1272 includes a conical surface 1290for engaging an annular valve seat 1292 formed on distributor housing1264 at fuel outlet 1278 when slidable piston 1272 is moved to the rightas shown in FIG. 56.

Slidable piston 1272 also includes a central orifice 1294 extendingthrough second end 1282 to fluidically connect central bore 1284 withfluid outlet 1018 regardless of the position of slidable piston 1272. Aplurality of first stage orifices 1296 extend through second end 1282from central bore 1284. First stage orifices 1296 are oriented inrelation to valve seat 1292 so that when flow limiting valve 1266 is inthe position shown in FIG. 56, hereinafter called the second stageposition, fuel flow from first stage orifices 1296 to fuel outlet 1278is blocked by the abutment of conical surface 1290 and valve seat 1292.Flow limiting valve 1266 includes a spring cavity 1298 formed betweenpiston 1272 and distributor housing 1264 for housing a biasing spring1300. An annular step 1302 formed on piston 1272 functions to provide aspring seat for spring 1300 which biases piston 1272 leftward asillustrated in FIG. 56 into a first stage position.

Bypass passage 1270 communicates at one end with fuel inlet 1276 viapiston chamber 1274 and at an opposite end with fuel outlet 1278.Slidable piston 1272 includes radial grooves 1304 in the end surface offirst end 1280 for permitting fuel to flow between fuel inlet 1276 andbypass passage 1270 when flow limiting valve 1266 is in the first stageposition. Rate shaping bypass valve 1268 is positioned along bypasspassage 1270 in a rate shaping valve cavity 1306. Rate shaping bypassvalve 1268 includes an elongated valve element 1308 having a conicalvalve surface 1310 for engaging an annular valve seat 1312 formed indistributor housing 1264. Rate shaping bypass valve 1268 is preferably atwo-position, two-way pressure balanced solenoid-operated valve whichincludes a bias spring 1314 positioned to bias valve element 1308 intothe closed position against valve seat 1312. A solenoid assemblyindicated at 1316 is used to move valve element 1308 to the right inFIG. 56 into a full flow, open position, separating conical valvesurface 1310 from annular valve seat 1312, thus establishing flowthrough bypass passage 1270. Rate shaping bypass valve 1268 mayalternatively be hydraulically operated.

In general, flow limiting valve 1266 functions to control or shape thepressure rate increase at the nozzle assembly during the initial stagesof an injection event, as represented by stages I and II in FIG. 57,while also controlling the return flow of fuel through the transfercircuit at the end of the injection event when the injection controlvalve 20 is connected to drain thereby minimizing cavitation in the fueltransfer circuit and associated fuel injection lines. Rate shapingbypass valve 1268 functions primarily to allow a rapid increase in thepressure rate when it is desirable to achieve maximum pressure at thenozzle assembly by providing an unrestricted flow path through fueltransfer circuit 1262 after the initial injection period as representedby stage III in FIG. 57.

More specifically, during operation, just before the start of aninjection event, injection control valve 19 is in the closed positionconnecting fuel transfer circuit 1262 to drain. At this time, flowlimiting valve 1266 is in its first stage position with first end 1280in abutment against distributor housing 1264 permitting fluidiccommunication between fuel inlet 1276 and fuel outlet 1278 via bothcentral orifice 1294 and first stage orifices 1296. Rate shaping bypassvalve 1268 is in the closed position under the force of bias spring 1314blocking flow through bypass passage 1270. Once injection control valve20 is energized to connect accumulator pressure to fuel transfer circuit1262, high pressure fuel initially flows through both central orifice1294 and first stage orifices 1296 creating an initial pressure increasedownstream of flow limiting valve 1266 and at the respective nozzleassembly as represented by stage I in FIG. 57. However, accumulator fuelpressure at fuel inlet 1276 acts on the end surface of first end 1280and on inner end 1286 of central bore 1284 to move slidable piston 1272to the right in FIG. 56, placing slidable piston 1272 in the secondstage position with conical surface 1290 in abutment with valve seat1292. Thus, fuel flow through first stage orifices 1296 is blocked whilea limited amount of fuel passes through central orifice 1294 to fueloutlet 1278 thus decreasing the rate at which fuel pressure at thenozzle assembly is increasing as represented by stage II in FIG. 57.After a predetermined period of time and preferably prior to the middleportion of the injection event, rate shaping bypass valve 1268 isenergized to the open position allowing full flow of fuel through bypasspassage 1270, causing a sharp increase in the fuel delivery pressure asrepresented by the upwardly sloping pressure rate of stage III in FIG.57. The pressure at the nozzle assembly quickly reaches a maximum leveluntil the end of the injection event as determined by the closing ofinjection control valve 20. Consequently, as shown in FIG. 57, rateshaping device 1260 creates an first stage of fuel injection (stage I)having a high pressure rate increase, a second stage of fuel injection(stage II) having a reduced pressure rate less than stage I and a thirdstage wherein the pressure rate increase is initially greater than stageII. By reducing the pressure rate increase at the nozzle assembly duringthe initial stages of injection, i.e. stage II, rate shaping device 1260also reduces the quantity of fuel delivered to the combustion chamberduring the initial stage which, in turn, advantageously reduces thelevel of emissions generated by the combustion process.

Upon closing, injection control valve 20 blocks fuel from theaccumulator while connecting fuel transfer circuit 1262 to drain. Aftera predetermined period of time, rate shaping bypass valve 1268 isde-energized and moved to the closed position by bias spring 1314.However, note that the pressure relief of fuel transfer circuit 1262downstream of rate shaping device 1260 can be controlled or shaped in avariety of ways depending on the timing of closing of rate shapingbypass valve 1268 in relation to the closing of injection control valve20. If the closing of rate shaping bypass valve 1268 is retarded ordelayed until a significant amount of time after the closing of fuelinjection control valve 20, bypass passage 1270 will function as theprimary relief passage allowing an intensive return flow of fuel todrain thus quickly relieving a substantial amount of fluid pressure fromthe downstream transfer circuit and respective fuel injection line whilea secondary relief flow is established through flow limiting valve 1266.However, by closing rate shaping bypass valve 1268 simultaneously with,or immediately after, the closing of injection control valve 20, primaryrelief occurs through flow limiting valve 1266. In both instances, oncerate shaping bypass valve 1268 closes, the fuel pressure at fuel inlet1276 becomes less than the fuel pressure in fuel outlet 1278. As aresult, the fluid forces acting on the end surface of piston 1272 atsecond end 1282, combined with the biasing force of spring 1300, becomegreater than the fluid forces acting on piston 1272 which tend to movepiston 1272 to the right in FIG. 56. Consequently, slidable piston 1272of flow limiting valve 1266 will immediately move leftward in FIG. 56into the first stage position communicating first stage orifices 1296with fuel outlet 1278, thus permitting fuel flow through flow limitingvalve 1266 via orifices 1294 and 1296. Central orifices 1294 and firststage orifices 1296 are large enough in diameter so that their combinedcross-sectional flow area creates the necessary return flow during thedrain event to insure sufficient fuel pressure relief at the nozzleassembly to prevent secondary injections. On the other hand, centralorifice 1294 and first stage orifices 1296 are small enough to provide acombined flow area designed to limit the return flow to a predeterminedlevel necessary to minimize cavitation in the circuit and injectionlines between flow limiting valve 1266 and the nozzle assemblies.Therefore, flow limiting valve 1266 functions as a variable flow valvewhen moved between the first stage and second stage positions toadvantageously utilize the flow limiting feature of central orifice 1294during the injection event to shape the pressure rate increase whileadvantageously controlling the return flow during the drain event toboth prevent secondary injections and minimize cavitation.

It should be noted that a single fixed orifice placed into the main flowwill cause a quite significant injection lag. A great portion of thislag is eliminated by the present rate shaping device which incorporatescentral orifice 1294 in a moving piston 1272. The swept volume of thispiston will result in no practical differential in the pressure tracecompared with a free line, until a certain pressure level. This levelmostly depends on the swept volume of the plunger, and the volume of thesystem pressurized. If the geometry ("d" diameter and "s" stroke; FIG.56) of piston 1272 is sized properly, the pressure can be maintainedslightly less than the opening pressure of the injector. This means thatthe invisible part of the injection rate has a "fast response" (no lag)and orifice 1294 starts dominating the event just from this pressurelevel, in order to shape the rate.

A further advantage of this design is realized by locating rate shapingbypass valve 1268 downstream of the injection control valve. Thisarrangement minimizes the leakage loss occurring through valve 1268.This leakage is four times less than it would be if valve 1268 wereplaced upstream of the injection control valve (assuming the duration is30 degrees crank angle and the engine is a six cylinder four strokeone).

Referring now to FIGS. 58 and 59, another rate shaping device 1320 isdisclosed in the context of the subject fuel pump system of the presentinvention including high pressure accumulator 12, injection controlvalve 20 and distributor 16 positioned along fuel transfer circuit 1322for delivering precise quantities of fuel through injection lines 1324for delivery to the engine cylinders (not shown) via respective nozzleassemblies 11. Rate shaping device 1320 includes high pressure deliverypassage 1328 of fuel transfer circuit 1322 connecting accumulator 12 toinjection control valve 20. At the beginning of the injection event,when injection control valve 20 moves to an open position fluidicallyconnecting accumulator 12 and high pressure delivery passage 1328 tofuel transfer circuit 1322 downstream of injection control valve 20, animmediate drop in fuel pressure is experienced in high pressure deliverypassage 1328 immediately upstream of injection control valve 20 while ahigh pressure fuel pulse from accumulator 12 quickly travels from theaccumulator to this low pressure region and then on to the nozzleassembly 11. Therefore, there is a time delay between the opening ofinjection control valve 20 and the arrival of the high pressure pulse atinjection control valve 20. The greater the distance the fuel pulse musttravel from accumulator 12 to injection control valve 20, the greaterthe time it will take for the fuel pressure at the control valve and,therefore, in the fuel injection line adjacent the nozzle assembly toincrease to the pressure rate necessary to achieve optimum high fuelpressure. Therefore, by increasing the distance between the accumulator12 and injection control valve 20, i.e., by lengthening high pressuredelivery passage 1328, rate shaping device 1320 of the presentembodiment slows down the rate of pressure increase at the nozzleassembly as represented by the pressure-time curve of FIG. 59.

Referring now to FIG. 60, another rate shaping device 1330 is disclosedwhich is similar to the embodiment shown in FIG. 58 in that a highpressure delivery loop 1332 having a length is used to control the timeit takes for the full unrestricted accumulator flow and resulting highpressure to reach nozzle assembly 11. However, in this embodiment, anorifice 1334 is positioned in a restricted flow passage 1336 so thathigh pressure delivery loop 1332 functions as a bypass around restrictedflow passage 1336. Again, like the previous embodiment, rate shapingdevice 1330 utilizes the fact that it takes time for pressure waves topropagate through high pressure delivery loop 1332 which delays thearrival of high pressure at nozzle assembly 11 and creates an initialperiod of injection having a low rate of pressure increase. However, inaddition, orifice 1334 functions to slow the rate of pressurization atthe nozzle assembly to the desired pressure rate. Therefore, orifice1334 can be selected with a predetermined cross-sectional flow areawhich provides a desired pressure rate during the initial injectionperiod. Moreover, orifice 1334 functions to dampen undesired pressurewaves fluctuating in the lines between the accumulator and injectioncontrol valve. Referring to FIG. 59, although for a given length of highpressure delivery loop 1332, the time delay (T) would remain constant,the pressure rate could be varied by selecting an appropriately sizedorifice 1334 to create a desired pressure rate change as represented bythe dashed lines 1338.

Reference is now made to FIG. 61 which discloses a rate shaping device1340 which is the same as rate shaping device 1330 of FIG. 60 exceptthat a rate-shaping or flow control valve 1342 is positioned in a highpressure bypass passage 1344 for directing flow around orifice 1334.Preferably, rate shaping control valve 1342 is a two-position, two-waypressure-balanced solenoid operated valve capable of being positioned ina closed position blocking flow through high pressure bypass passage1344 and an open position permitting flow. Rate shaping control valve1342 permits the time delay (T) shown in FIG. 59 to be accuratelycontrolled and varied by electronically controlling and adjusting theopening and closing of rate control valve 1342.

The rate shaping devices shown in FIGS. 56-62 and discussed hereinabovehave the ability to be connected to nozzle assemblies such as thetwo-spring nozzle assembly produced by Bosch or the piston in the nozzleassembly as conceived by AVL which are intended to reduce the fuelquantity delivered during the first part of injection. When these nozzleassemblies designs are connected to the accumulator rate shapingconcepts of the present invention, the coupling of the two producesfurther reductions in the quantity of fuel injected in the beginning ofthe injection event.

Reference is now made to FIGS. 62a and 62b which disclose a rate shapingcoupling 1350 for integrating the rate shaping devices disclosed inFIGS. 60 and 61 into a fuel system while also providing a housing forreceiving an edge filter. Rate shaping coupling 1350 includes agenerally cylindrical housing 1352 having an inlet portion 1354, anoutlet bypass portion 1356, and a central feed bore 1358 extendingthrough both inlet portion 1354 and outlet bypass portion 1356. Housing1352 further includes a bypass return portion 1360 and a dischargeportion 1362 integrally formed with inlet portion 1354 and outlet bypassportion 1356. Discharge portion 1362 includes a feed passage 1364extending inwardly through portion 1362 toward central feed bore 1358. Aflow restricting orifice 1366, equivalent to orifice 1334 of FIGS. 60and 61, is positioned at the inner end of feed passage 1364 to connectfeed passage 1364 to central feed bore 1358. As illustrated in FIG. 62b,bypass return portion 1360 includes a return passage 1368 which extendsthrough housing 1352 to connect with feed passage 1364 downstream oforifice 1366. Referring again to FIGS. 62a and 62b, inlet portion 1354is connected by a high pressure tube fitting 1370 to a fuel feed tube1372 which delivers fuel from the accumulator (not shown). Outlet bypassportion 1356 is connected to one end of a bypass loop or tuberepresented at 1374 while the opposite end of bypass loop 1374 isattached to bypass return portion 1360. Bypass loop 1374 is theequivalent of delivery loop 1332 and bypass passage 1344 disclosed inFIGS. 60 and 61, respectively. Therefore, rate shaping control valve1342 of FIG. 61 may be positioned along bypass loop 1374. Also, an edgefilter 1376 is positioned in central feed bore 1358 of housing 1352adjacent inlet portion 1354. A support pin 1377 is positioned in centralbore 1358 in compressive abutment between edge filter 1376 and one endof feed tube 1372 for securing edge filter 1376 in central feed bore1358. Support pin 1377 includes axial grooves 1379 for permitting fuelflow through central feed bore 1358 to bypass loop 1374. The edge filter1376 functions to remove small particles, such as metal shavings, fromthe fuel to prevent the particles from reaching the injection controlvalve and distributor positioned downstream. Therefore, rate shapingcoupling 1350 provides a compact, effective device for implementing therate shaping devices of FIGS. 60 and 61 while also providing a easilyaccessible yet effective housing for an edge filter.

Reference is now made to FIGS. 63a-69 which disclose various devices forminimizing cavitation in the fuel transfer circuit and high pressureinjection lines while also minimizing the possibility of a secondaryinjection. Cavitation, i.e. vapor pockets or voids, in the transfercircuit and injection lines leading to the nozzle assemblies results ininsufficient injection pressure and unpredictable, uncontrollablevariations in both fuel quantity and timing of injection. Cavitation isespecially prone to occur in high pressure lines of fuel systems wheresuch lines are connected to a low pressure drain on a cycle by cyclebasis such as in the fuel pumping system of the present invention. Thefollowing devices advantageously control cavitation by 1) minimizing theoccurrence of cavitation by restricting the return or reverse fuel flowduring the draining event and/or 2) refilling the injection lines withfuel after each draining event and prior to the succeeding injectionevent. Specifically, the cavitation control devices disclosed in theembodiments shown in FIGS. 64a-64e minimize cavitation by restrictingthe return fuel flow during the drain event while the devices disclosedin FIGS. 63a, 63b and 69 minimize the effects of cavitation by primarilyrefilling the downstream lines with fuel.

Referring initially to the embodiment disclosed in FIGS. 63a and 63b, acavitation control device indicated generally at 1400 is formed in adistributor housing 1402 of a distributor 1404. FIG. 63a alsoillustrates an injection control valve 1406, a low pressure accumulator1408 mounted in a spacer housing 1410, a two-piece gear pump housing1412, 1414 and a boost or gear pump 1416. These various components aresubstantially the same as the embodiment described hereinabove withregards to FIG. 30 with the exception of the addition of cavitationcontrol device 1400. Cavitation control device 1400 includes an axialpassage 1418 extending from the outlet of boost pump 1416 adjacent lowpressure accumulator 1408 through spacer housing 1410, two-piece gearpump housing 1412, 1414 and distributor housing 1402. Axial passage 1418terminates approximately midway through distributor housing 1402 forconnection with a delivery passage 1420 extending radially inward at anangle through distributor housing 1402 and a stationary shaft sleeve1422 surrounding a rotary distributor shaft 1424. The most inward end ofdelivery passage 1420 continuously communicates with an annular groove1426 formed in the outer surface of distributor shaft 1424. A crosspassage 1428 extends diagonally from annular groove 1426 through thecenter axis of distributor shaft 1424 to the opposite side ofdistributor shaft 1424. Cross passage 1428 connects annular groove 1426to a refill port 1430 formed in the outer surface of distributor shaft1424. As shown in FIGS. 63a and 63b, refill port 1430 is positioned in acommon vertical plane with an injection port or window 1432 whichsequentially communicates with fuel receiving passages 1434 equallyspaced around the circumference of rotor bore 1436. As discussedhereinabove in relation to the embodiment of FIG. 5, injection controlvalve 1406 supplies fuel through a fuel transfer circuit to injectionport 1432 during the window of opportunity to create an injection event.The fuel transfer circuit includes passages 1438 and 1440 formed indistributor housing 1402 and shaft sleeve 1422, respectively, an annularsupply groove 1442 formed in distributor shaft 1424 and a transferpassage 1444 extending from annular supply groove 1442 diagonallythrough distributor shaft 1424 to connect with injection port 1432. Asshown in FIG. 63b, at the end of the injection event, as distributorshaft 1424 rotates in the clockwise direction, injection port 1432 willmove out of communication with a given fuel receiving passage 1434. Asdistributor shaft 1424 continues to rotate, refill port 1430 will bemoved into fluidic communication with the receiving passage 1434 throughwhich an injection event previously occurred. As a result, low pressurefuel from the outlet of boost pump 1416 is delivered via passages 1418,1420, annular groove 1426 and cross passage 1428 to the respective fuelreceiving passage 1434. Each fuel receiving passage 1434 is connected toa nozzle assembly 1445 of an associated engine cylinder by a respectiveinjection passage 1446 formed in distributor housing 1402, a respectiveinjection bore 1448 formed in an outlet fitting 1450 and a correspondinginjection line 1452 connected at one end to outlet fitting 1450 and atan opposite end to nozzle assembly 1445. In this manner, cavitationcontrol device 1400 ensures that each injection circuit connectingdistributor 1404 to a respective nozzle assembly is refilled with lowpressure fuel before the next injection event thus minimizing cavitationinduced variations in fuel quantity and timing of injection. Moreover,since boost pump fuel pressure is maintained at a relatively constantlevel, all injection lines are pressurized to approximately the samefuel pressure level for each injection event thus adding to thepredictability of fuel metering and timing.

FIGS. 63a and 64a also illustrate another device for minimizingcavitation indicated generally at A. This embodiment includes a reverseflow restrictor valve 1460 positioned along the fuel transfer circuit1462 between injection control valve 1406 and distributor 1404. Reverseflow restrictor valve 1460 includes a movable valve member 1464, aninsert 1466 and a support ring 1468 supported in a recess 1470 formed indistributor housing 1402. The inner end of recess 1470 communicates withone end of passage 1438 via an outlet 1463 for delivering fuel todistributor 1404. A transfer passage 1472 formed in an injection controlvalve housing 1474 includes an inlet 1475 positioned to open into recess1470 when injection control valve housing 1474 is positioned adjacentdistributor housing 1402. A spacer plate 1476 is positioned betweeninjection control valve housing 1474 and distributor housing 1402.Spacer plate 1476 includes an opening 1478 through which reverse flowrestrictor valve 1460 extends. Support ring 1468 is positioned againstthe inner end of recess 1470 around outlet 1463 for supporting insert1466. Insert 1466 is positioned in recess 1470 in compressive abutmentwith support ring 1468 at one end and injection control valve housing1474 at an opposite end. Insert 1466 includes an annular base 1480positioned in abutment with support ring 1468 and wall portions 1482extending upwardly from base 1480 to abut with housing 1874. Wallportions 1482 form a valve cavity 1484 for receiving valve member 1464.A bore 1486 extending through base 1480 connects outlet 1463 to valvecavity 1484. Radial grooves 1488 formed in the upper portion of base1480 extend from bore 1486 radially outward to connect with respectiveslots 1490 separating wall portions 1482.

Movable valve member 1464 is generally doughnut shaped and sized with anappropriate outer diameter to permit movement in valve cavity 1484 alonga vertical axis while wall portions 1482 provide lateral support tovalve member 1464. A valve seat 1492 formed around inlet opening isadapted for sealing engagement by valve member 1464 when valve member1464 is moved upwardly into a restricting position. Valve member 1464may move downward into abutment with the inner surface of cavity 1484into an open position as shown in FIG. 64. Valve member 1464 is alsosized with an appropriate width to create an axial gap 1493 forpermitting fuel flow from inlet 1475 to slots 1490 when valve member1464 is in the open position. Valve member 1464 includes a centralorifice 1494 for permitting fluidic communication between inlet 1475 andoutlet 1463 when valve member 1464 is in the restricting position.

The high pressure joints formed by the abutment of injection controlvalve housing 1474, spacer plate 1476 and distributor housing 1402 aresealed using several devices to prevent high pressure fuel leakage.First, an annular sealing ring, i.e., a C-ring, 1496 is positioned incompressive abutment between injection control housing 1474 anddistributor housing 1402 within opening 1478. In addition, opposingannular fuel collection grooves 1498 are formed in each housing 1474,1402 radially outward from sealing ring 1496 for collecting any fuelleaking by sealing ring 1496. A drain passage 1500 extends from one fuelcollection groove for draining collected fuel to drain (not shown). Anequalizing passage 1502 extends through spacer plate 1476 to connect theopposing fuel collection grooves 1498, thereby permitting fuel collectedin both grooves to be directed to drain. Third, a pair of opposingannular O ring grooves 1504 are formed in the housings 1474 and 1402radially outward from fuel collection grooves 1498 for additionalsealing.

During operation, at the beginning of an injection event when injectioncontrol valve 1406 moves into an open position supplying high pressurefuel from the accumulator (not shown) to transfer passage 1472, valvemember 1464 of reverse flow restrictor valve 1460 moves under the forceof the high pressure fuel into abutment against the inner surface ofvalve cavity 1484 into an open, full flow position. In this openposition, fuel flows from transfer passage 1472 through axial gap 1493,slots 1490, and into bore 1486 for delivery to distributor 1404 viaoutlet 1463 and passage 1438. Fuel from transfer passage 1472 also flowsthrough central orifice 1494 for delivery to the distributor. Valvemember 1464 is sized so that the effective flow area of axial gap 1493,in combination with the effective flow area of central orifice 1494,creates substantially unrestricted flow through restrictor valve 1460.At the end of the injection event, when injection control valve 1406moves into a drain position connecting transfer passage 1472 to drain,the fuel pressure in transfer passage 1472 immediately becomes less thanthe pressure in passage 1438 and bore 1486. As a result, a return orreverse flow of fuel flows from passage 1438 and other downstreampassages including the respective fuel injection line, in a reversedirection through flow restrictor valve 1460 toward injection controlvalve 1406. As discussed hereinabove, without the use of flow restrictorvalve 1460, vapor pockets or voids (cavitation) may form in the transferpassages and injection line between the injection control valve 1406 andthe nozzle assemblies. However, reverse flow restrictor valve 1460 helpsto minimize cavitation by permitting valve member 1464 to move into arestricting position against valve seat 1492. In the restrictingposition, valve member 1464 blocks reverse fuel flow through annular gap1493 while permitting a restricted flow of fuel through central orifice1494. Central orifice 1494 has an effective cross sectional flow areawhich permits a reverse flow of fuel sufficient to allow adequatepressure relief of the passages between restrictor valve 1460 and thenozzle assembly to permit the nozzle valve element (not shown) of thenozzle assembly to close resulting in predictable timing and metering ofinjection while restricting fuel flow to create an optimal back pressurefor minimizing cavitation.

Now referring to FIG. 64b, another embodiment of the flow restrictorvalve is disclosed which is similar to the embodiment of FIG. 64a inthat valve member 1464 including central orifice 1494 is positioned in arecess 1470 formed in distributor housing 1402. However, in theembodiment shown in FIG. 64b, wall portions 1510 are formed integrallywith distributor housing 1402 in the inner end of recess 1470. Wallportions 1510 extend radially inward to define a central bore 1512connected to outlet passage 1514 for directing fuel to distributor 1404.Wall portions 1510 are separated by slots 1516 communicating withcentral bore 1512. In this embodiment, valve member 1464 is sized toform both an axial gap 1518 between its upper flat surface and annularvalve seat 1492, and an annular radial gap 1520 between its outercircumferential surface and the inner surface of recess 1470. Whenpositioned in the open, full flow position as shown in FIG. 64b, fuelflows from transfer passage 1472 through axial gap 1518 and radial gap1520 into central bore 1512 via slots 1516 for delivery to distributor1404 via outlet passage 1514. Valve member 1464 functions in the samemanner as that described with respect to the embodiment of FIG. 64a whenmoved into a restricting position against annular valve seat 1492 torestrict the reverse flow of fuel, thus slowing down the pressure decayin the fuel transfer circuit and injection lines between valve member1464 and nozzle assembly thereby preventing excessive cavitation. Also,it should be noted that this embodiment does not include a spacer plate1476. Moreover, sealing ring 1496 is positioned in a single ring groove1522 formed in injection control valve housing 1474. Also, only a singlefuel collection groove 1524 and a single O-ring groove 1526 for housingO-ring 1528, are needed since only one high pressure joint is formedbetween housings 1474 and 1402.

Reference is now made to FIG. 64c which illustrates yet anotherembodiment of a cavitation control device which is the same as theembodiment shown in FIG. 64b except that a conical shaped recess 1530 isformed in the upstream side of a movable valve member 1532 adjacentannular valve seat 1492. Central orifice 1534 extends through movablevalve member 1532 connecting conical shaped recess 1530 to central bore1512. Conical shaped recess 1530 functions to decrease the surface areaof valve member 1532 contacting valve seat 1492 thereby improving theseating of valve member 1532 against valve seat 1492.

Referring now to FIG. 64d, a fourth embodiment of the reverse flowrestrictor valve is disclosed which includes a cylindrical jumper tube1540 positioned in a recess 1542 formed in both distributor housing 1402and injection control valve housing 1474. Jumper tube 1540 is preferablyfixedly attached to the inner wall of recess 1542 by a press fitconnection whereby the outer diameter of jumper tube 1540 is slightlylarger than the inner diameter of the portion of recess 1542 formed indistributor housing 1402 prior to assembly. The portion of recess 1542formed in injection control valve housing 1474 has a slightly largerinner diameter than the outer diameter of jumper tube 1540 to create aclearance therebetween for permitting fuel leakage to flow to drain.Jumper tube 1540 abuts the upstream end of recess 1542 and extends intodistributor housing 1402 terminating prior to the opposite end of recess1542 to form a valve cavity 1544 for receiving a movable valve member1546. Jumper tube 1540 includes a center bore 1548 for permitting fluidflow between transfer passage 1472 and valve cavity 1544. Jumper tube1540 also includes a valve seat 1550 formed on its end wall adjacentvalve cavity 1544 for engagement by movable valve member 1546. Movablevalve member 1546 includes a conical shaped recess 1552 formed in oneend adjacent valve seat 1550 and a central orifice 1554 extending fromconical shaped recess 1552 through valve member 1546 to connect withoutlet passage 1556. Inner annual wall portions 1558 formed aroundoutlet passage 1556 extend toward movable valve member 1546. Wallportions 1558 are separated by slots 1560 extending radially outwardfrom outlet passage 1556 to connect with an outer annular groove 1562.Axial grooves 1564 are formed in the outer surface of movable valvemember 1546 around its circumference. When movable valve member 1546 ismoved by upstream fuel pressure into the open position as shown in FIG.64d, fuel is permitted to flow from center bore 1548 into valve cavity1544 and through axial grooves 1564 into outlet passage 1556 via annulargroove 1562 and slots 1560. The advantages and operation of thisembodiment of the reverse flow restrictor valve are the same as theprevious embodiments.

FIG. 64e illustrates yet another embodiment of the reverse flowrestrictor valve of the present invention which includes a cylindricaljumper tube 1570 positioned in a recess 1572 similar to that of theprevious embodiment. However, jumper tube 1570 and a support ring 1574are held in end to end compressive abutment in recess 1572. Jumper tube1570 includes a center bore 1576 which communicates at one end withtransfer passage 1472 and at an opposite end with an outlet passage1578. In this embodiment, a movable valve member 1580 is positioned in arecess 1582 formed in the upstream end of center bore 1576. Movablevalve member 1580 includes a conical shaped recess 1584 formed in itsupstream end and a central orifice 1586 which fluidically connectsrecess 1584 to center bore 1576. In this embodiment, axial grooves 1588are formed in the inner surface of jumper tube 1570 along the entirelength of tube 1570. In this manner, during the injection event, whenmovable valve member 1580 is positioned in the full flow open positionas shown in FIG. 64e, fuel flows from passage 1472 through axial grooves1588 to outlet passage 1578 via center bore 1576. In addition, movablevalve member 1580 is spring biased into the flow restricting position bya bias spring 1590 positioned in center bore 1576. Bias spring 1590assists in moving the valve member 1580 into the flow restrictingposition upon the connection of fuel transfer passage 1472 to drain atthe end of the injection event.

Referring now to FIG. 65, another embodiment of the cavitation controldevice of the present invention includes an auxiliary supply of fuel,indicated generally at 1600, delivered to the drain passage 1602 of theinjection control valve 1604. As explained hereinabove in relation tothe fuel system of the present invention, injection control valve 1604operates to fluidically connect accumulator 1606 to distributor 1608 todefine an injection event. Injection control valve 1604 ends theinjection event by connecting fuel transfer passage 1610, and thereforethe corresponding injection line connected by distributor 1608, to drainpassage 1602 permitting fuel flow from transfer passage 1610 andinjection line 1612 to a drain 1614. As noted hereinabove, this drainingevent may cause cavitation in passage 1610 and the respective downstreampassages. The embodiment shown in FIG. 65 minimize the effects ofcavitation in passage 1610 and injection line 1612 during the injectioncut off event by supplying auxiliary fuel at a relatively low pressure,i.e., 300 psi, to the transfer and injection passages between injectioncontrol valve 1604 and nozzle assembly 1616 thereby refilling thepassages prior to the next injection event. The auxiliary fuel alsominimizes cavitation slowing down the draining of fuel during thedraining event thereby preventing excessive pressure decay in thedownstream passages. In this embodiment, the auxiliary fuel is suppliedby boost pump 1618 which supplies low pressure fuel to high pressurepump 1620 for delivery to accumulator 1606. Auxiliary fuel passage 1622is connected at one end to the downstream side of boost pump 1618, forexample, directly into transfer passage 1624 connecting boost pump 1618and high pressure pump 1620. The opposite end of auxiliary fuel passage1622 is connected to drain passage 1602. A restriction orifice 1626 ispositioned in drain passage 1602 downstream of the connection ofauxiliary fuel passage 1622. Restriction orifice 1626 functions toreduce the quantity of auxiliary fuel returned to drain 1614 therebyminimizing pumping losses.

Reference is now made to FIG. 66 showing another embodiment of thecavitation control device of the present invention which includes apressure regulator 1630 positioned within the drain passage 1632extending from injection control valve 1634. Pressure regulator 1630includes a cylinder 1636 which forms a cavity 1638 connected at one endto drain passage 1632. Pressure regulator 1630 also includes a piston1640 slidably mounted in cavity 1638 so as to divide cavity 1638 into aninlet chamber 1642 for receiving fuel from drain passage 1632 and abiasing chamber 1644. The outer cylindrical surface of piston 1640 formsa sufficiently close sliding fit with the inside surface of cylinder1636 to form a fluid seal between the surfaces to substantially preventfuel leaking from inlet chamber 1642 to biasing chamber 1644. A biasspring 1646 is positioned in biasing chamber 1644 for biasing piston1640 toward inlet chamber 1642. A leak-by drain passage 1648 isconnected to spring chamber 1644 to direct any fuel accumulating inspring chamber 1644 to drain. A high pressure relief passage 1650 isconnected to cavity 1638 along the length of cylinder 1636 between inletchamber 1642 and spring chamber 1644. Bias spring 1646 normally biasespiston 1640 to the left in FIG. 66 so that the outer cylindrical surfaceof piston 1640 covers relief passage 1650 preventing flow from drainpassage 1632 to relief passage 1650 via inlet chamber 1642. During aninjection event, injection control valve 1634 fluidically connectsaccumulator 1652 to distributor 1654, while blocking fuel flow betweenfuel transfer circuit 1656 and drain passage 1632. During this time,piston 1640 will normally block relief passage 1650 since no highpressure fuel exists in inlet chamber 1642. Once the injection event iscomplete, and the injection control valve 1634 moves into a drainposition connecting fuel injection passages 1658 and a respective fuelinjection line 1660 to drain passage 1632, high pressure fuel flowsthrough drain passage 1632 into inlet chamber 1642. The high pressure ofthe fuel in inlet chamber 1642 acts on the end face 1662 of piston 1640creating a force which tends to move piston 1640 to the right in FIG.66. However, bias spring 1646 will resist the rightward movement ofpiston 1640 thereby creating a back pressure in the fuel transferpassages and respective injection line. Once the pressure of the fuel ininlet chamber 1642 rises to a predetermined level sufficient to overcomethe bias force of spring 1646, piston 1640 will move to the right inFIG. 66, uncovering high pressure relief passage 1650 thereby allowingfuel from inlet chamber 1642, transfer passage 1658 and other downstreamlines including injection line 1660 to flow in the reverse directionthrough drain passage 1632 and relief passage 1650. Once the fuelpressure in the drain passage decreases to below a predetermined level,piston 1640 will move to the left in FIG. 66, under the force of biasspring 1646, blocking fuel flow through relief passage 1650. Inletchamber 1642 functions as an accumulator for accumulating fuel forrefilling the injection lines to minimize the effects of any cavitation.The force of piston 1640 against the accumulated fuel in inlet chamber1642 pumps fuel into the fuel transfer passages and injection lines at apredetermined low pressure level thereby refilling any voids or vaporpockets unexpectedly formed in the transfer passages and injection linesduring the draining event. Also, the effective cross sectional area ofend face 1662 and the bias force of spring 1646 are carefully chosen tocreate a draining effect corresponding to the optimal rate of pressuredecay in the injection lines and passages connected to drain to minimizecavitation. Also, a conventional pressure regulator could be used tomaintain a back pressure without the advantages of an accumulated volumeof fuel for refilling the injection lines.

In addition, the pressure regulator 1630 of FIG. 66 may be combined withcavitation control device 1400 of FIGS. 63a and 63b to advantageouslyminimize cavitation. Drain passage 1632 in FIG. 66 connecting theinjection control valve to the pressure regulator 1630 is subject topressure wave fluctuations due to the repeated relief of relatively highinjection pressure into the drain passage caused by the operation of theinjection control valve. These pressure wave fluctuations may betransmitted to the injection lines 1660 during refill adverselyaffecting the refill procedure and subsequent injections. However, bycombining the embodiments of FIGS. 63a and 66, the relatively constantboost pump fuel pressure 416 of cavitation control device 1400, which isfree of pressure wave fluctuations, is used to more effectively refillthe injection lines downstream of the distributor without subjecting theinjection lines to pressure wave fluctuations and the associated adverseeffects.

Reference is now made to FIG. 67 disclosing another embodiment of thecavitation control device of the present invention which is similar tothe previous embodiment and therefore like components will be referredto with the same reference numerals used in FIG. 66. In this embodiment,a pressure regulator 1666 includes a piston 1668 biased toward inletchamber 1642 by the pressure of fuel supplied from accumulator 1652. Abiasing fluid passage 1670 is connected to accumulator 1652 at one endand biasing chamber 1644 at an opposite end. A biasing pin 1672 isslidably mounted in biasing fluid passage 1670 adjacent biasing chamber1644. An inner end 1674 of biasing pin 1672 extends into biasing chamber1644 into abutment with one end of piston 1668. An outer end 1676 ofbiasing pin 1672 is exposed to accumulator fuel at extremely highpressure. By choosing the proper effective cross sectional area of theouter end 1676 of biasing pin 1672, pressure regulator 1666 can be usedin the same manner as the embodiment of FIG. 66 to provide sufficientdraining of the fuel transfer circuit and injection lines to endinjection while both maintaining an optimum back pressure necessary tominimize cavitation and supplying low pressure fuel to the fuel passageand respective injection line during the last portion of the drainingevent to refill the injection passages and lines. In addition, thisembodiment includes a refill passage 1678 connecting drain passage 1632to each of the fuel injection lines 1660 via distributor 1654 forrefilling the injection passages and injection line 1660 betweendistributor 1664 and nozzle assembly after the draining event prior tothe next injection event. Refill passage 1678 is connected to each ofthe injection lines 1660 via passages (not shown) formed in thedistributor housing and rotating shaft similar to the passages disclosedin FIGS. 63a and 63b with respect to cavitation control device 1400except that delivery passage 1420 would be connected to refill passage1678. Thus, subsequent to an injection event, refill port 1430 shown inFIG. 63a sequentially connects each injection line to refill passage1678 permitting fuel in inlet chamber 1642 to flow to the respectiveinjection line. The biased piston 1668 of pressure regulator 1666maintains a back pressure in refill passage 1678 during the injectionevent when injection control valve 1634 blocks flow through drainpassage 1632. Thus, pressure regulator 1666 functions to pump fuel backinto fuel injection lines 1660 via refill passage 1678 to fill the vaporpockets or voids possibly formed during the previous injection cut offevent and prior to the next injection, thereby insuring accurate andpredictable and timing of the injection. Alternatively, a refill groove1679 may be formed in distributor shaft 1424. Refill groove extendsaround the circumference of shaft 1424 a sufficient angular distance tofluidically connect, during a portion of each injection period, the fuelreceiving passages 1434 which are not connected to injection port 1432.Thus, refill groove 1679 permits refilling of receiving passages 1434and corresponding downstream lines between injection events andequalization of the initial fuel pressure in these passages prior toeach injection event to insure controllable and predictable fuelmetering from one injection period or engine cycle to the next.

Referring now to FIG. 69, another embodiment of the cavitation controldevice of the present invention is disclosed. This embodiment combinesthe spring biased pressure regulator 1630 of FIG. 66 with the refillpassage 1678 disclosed in FIG. 67. Therefore, the functioning andadvantages of this embodiment are substantially the same as the previoustwo embodiments.

As can be appreciated from the discussion set forth hereinabove, thepresent invention advantageously provides a fuel system comprised of anelectronically controllable, high pressure fuel pump assembly includinga pump, accumulator and distributor combined with an electricallyoperated pump control valve and an injection control valve mounted onthe unitized assembly to form a highly integrated fuel system whichprovides superior emissions control and improved engine performance andwhich may be designed, built and installed either for an original orpre-existing engine design with minimal modification of the pre-existingdesigns. This highly integrated fuel system is capable of achieving veryhigh injection pressures, i.e., 5000-30,000 psi and preferably in therange of 16,000-22,000 psi with precise control over injection quantityand timing in response to varying engine conditions while allowing forthe provision of redundant fail safe electronic components, and improvedengine efficiency at overall reduced costs with respect to competingprior art systems.

The present fuel system also offers the advantage of a highly compact,integrated fuel pump assembly by providing a pump housing having atleast one pump cavity oriented in a radial direction, and an accumulatormounted on the pump housing. Such accumulator may provide an overhang ineither the lateral and/or axial direction and a pump control valvemounted on the overhang portion of the accumulator housing adjacent thepump housing. In addition, the accumulator housing is mounted on thepump housing at one end of the pump housing to form a cantileveredlateral overhang such that the overhang forms an offset transverseprofile for the fuel pump assembly to complement the irregulartransverse profile of the internal combustion engine on which the fuelassembly is designed to be mounted.

The present fuel system also advantageously provides a unitized, singlepiece fuel pump housing containing plural outwardly opening pumpcavities, a radially enclosed drive shaft, a pump head engaging surfaceand plural tappet guiding surfaces within corresponding pump cavitieswherein the tappet guiding surfaces, head engaging surface and driveshaft mounting surfaces are the only surfaces requiring close machiningto create adequate alignment between the drive shaft and the cooperatingfuel pumping elements of the pump. Moreover, by providing a pump headmounted on the pump housing opposite the drive shaft and a pump unitretained in the pump head by means of a retainer which causes the pumpunit to extend into the pump cavity of the pump housing in spaced apartnon-contacting relationship with the pump housing, the present inventionallows the pump unit to be relatively easily removed and replaced toprovide inexpensive overhaul of the pump assembly and/or the ability toswitch pump units to adjust the effective displacement of the fuel pumpassembly.

Moreover, the fuel system of the present invention minimizes the numberof fuel leakage sites by reducing the system components and providingfail safe redundant low pressure fuel drains throughout the system tocatch and return to the fuel system any fuel which may leak throughprimary seal areas. Also, the present fuel system may include both twopump control valves and two injection control valves to allow onerespective valve to take over if the other respective valve shouldbecome disabled.

The present invention also provides an improved accumulator containing alabyrinth of interconnecting chambers wherein the chambers areelongated, cylindrical in shape and positioned in generally parallelrelationship intersecting a vertical plane through the accumulatorhousing in a two dimensional array. The accumulator chambers arespecifically oriented to minimize the physical dimensions of theaccumulator housing while being dimensioned to create a minimum totalvolume sufficient to prevent fuel pressure from dropping more than fivepercent during any injection event depending upon such factors as thecompressibility of the fuel, the operating pressure of the fuel, themaximum potential required injection volumes, timing range and injectionduration selected for the engine, the maximum effective displacement ofeach pump unit, the fuel leakage of the system, the compression of thefuel in the fuel lines, and the fuel lost to drain during valve membertravel between fully opened and fully closed positions.

The disclosed invention provides a variety of additional features suchas (1) the integration of a rotatable pump and distributor with a singledrive shaft assembly; (2) the provision of a distributor includingaxially slidable spool valves in combination with a separate injectioncontrol valve; (3) the provision of a variety of pump head/accumulatordesigns for accommodating pump control valves and check valves; (4) theprovision of ultra-compact pump head and integral pump chamber designs;(5) the provision of a transversely oriented pump control valve forreducing to an absolute minimum the trapped volume within theaccumulator; (6) the provision of a pump unit and transverse pumpcontrol valve mounted in the barrel of the pump unit; (7) variousaccumulator designs for simplifying the formation and manufacture of theaccumulator; (8) the provision of a separately mounted accumulator; (9)the provision of various edge filter mounting concepts for use withinthe disclosed fuel system; and (10) the provision of rate shaping andcavitation control devices within the disclosed fuel system.

Industrial Applicability

The compact high performance fuel system of the present invention, andthe components thereof, may be used in a variety of combustion enginesof any vehicle or industrial equipment requiring accurate and reliablehigh pressure fuel delivery. However, the high performance fuel systemof the present invention is particularly useful with small and mediumdisplacement diesel truck engines and especially adaptable to existingdiesel engine designs without major engine modifications.

We claim:
 1. An electronically controllable, high pressure fuel pumpassembly for supplying fuel at a predetermined pressure through pluralfuel injection lines to the corresponding cylinders of a multi-cylinderinternal combustion engine, comprising(a) a unitized assembly adapted tobe mounted on the engine, said unitized assembly includingi. pump meansfor pressurizing fuel above the predetermined pressure, said pump meansincluding a pump housing having mounting means for mounting saidunitized assembly on the engine, ii. an accumulator means foraccumulating and temporarily storing fuel at high pressure received fromsaid pump means, said accumulator means including an accumulator housingcontaining at least one accumulator chamber, said accumulator housingbeing mounted on said pump housing, and iii. a fuel distributor meansfor enabling sequential periodic fluidic communication between saidaccumulator chamber and the engine cylinders, said distributor meansincluding a distributor housing being mounted on said pump housing; (b)a first solenoid operated pump control valve for controlling said pumpmeans to maintain a desired pressure of fuel in said accumulatorchamber, said first solenoid operated pump control valve by beingmounted on said unitized assembly; and (c) a first solenoid operatedinjection control valve for controlling the timing and quantity of fuelinjected into each engine cylinder in response to engine operatingconditions, said first solenoid operated injection control valve beingmounted on said unitized assembly.
 2. The electronically controlled,high pressure fuel pump assembly of claim 1, further including a secondsolenoid operated pump control valve for controlling said pump means tomaintain the desired pressure of fuel in said accumulator chamber evenif said first solenoid operated pump control valve becomes disabled. 3.The electronically controlled, high pressure fuel pump assembly of claim1, further including a second solenoid operated injection control valvefor controlling the timing and quantity of injection into each enginecylinder even if said first solenoid operated injection control valvebecomes disabled.
 4. The fuel pump assembly of claim 1, wherein saidpump means includes plural pump chambers, plural pump plungers mountedfor reciprocal motion within said pump chambers, and wherein saidassembly further includes plural solenoid operated pump control valvescorresponding in number to said pump chambers, said solenoid operatedpump control valves being connected with said pump chambers,respectively, for controlling the effective displacement of each saidassociated pump plunger.
 5. The fuel pump assembly of claim 4, furtherincluding means for generating a pressure signal representative of thepressure of the fuel in said accumulator means and control means forcontrolling said solenoid operated pump control valves to adjust theeffective displacement of said pump plungers in response to saidpressure signal to cause the pressure of fuel in said accumulator meansto equal said predetermined pressure.
 6. An electronically controllable,fail safe, high pressure fuel pump assembly for supplying fuel at apredetermined pressure through plural fuel injection lines to thecorresponding cylinders of a multi-cylinder internal combustion engine,comprising(a) pump means for pressurizing fuel above the predeterminedpressure, said pump means including plural positive displacement pumpelements having variable displacement capability, (b) an accumulatormeans for accumulating and temporarily storing fuel at high pressurereceived from said pump means, said accumulator including at least oneaccumulator chamber arranged to receive fuel from all said positivedisplacement pump elements, (c) a fuel distributor means for enablingsequential periodic fluidic communication between said accumulatorchamber and the engine cylinders, (d) at least a pair of associatedsolenoid operated pump control valves for controlling the effectivedisplacement of said pump elements to cause said pump elements to sharethe pumping load necessary to maintain a desired pressure of fuel insaid accumulator chamber, (e) a first solenoid operated injectioncontrol valve for normally controlling the timing of one portion of thequantity of fuel injected into each engine cylinder during eachinjection event, and (f) electronic control means for controlling theoperation of said pump control valves to allow substantially normalengine operation should one of said pump control valves become disabledby causing the associated pump control valve to take over the functionof the disabled pump control valve.
 7. The fuel pump assembly of claim6, further including a second solenoid operated injection control valveassociated with said first solenoid operated injection control valve fornormally controlling the timing of another quantity of fuel injectedinto each engine cylinder during each injection event wherein saidelectronic control means operates to control said injection controlvalves to allow at least "imp-home" operation of said engine should oneof said injection control valves become disabled by causing theassociated injection control valve to take over the function of thedisabled injection control valve.
 8. A compact, high pressure fuel pumpassembly for supplying fuel to a multi-cylinder internal combustionengine, comprisinga pump housing having minimal extent in mutuallyperpendicular lateral, radial and axial directions, said pump housingcontaining at least one pump cavity having a first pump axis extendingin the radial direction and a drive shaft cavity adjacent one end ofsaid pump cavity having a drive axis extending in the axial direction;adrive shaft mounted within said drive shaft cavity for rotation aboutsaid drive axis; a pump plunger mounted within said pump cavity forreciprocatory motion along said first pump axis in response torotational movement of said drive shaft; and an accumulator housingcontaining at least one elongated accumulator chamber for accumulatingand temporarily storing fuel at high pressure, said accumulator housingbeing mounted on said pump housing adjacent the other end of said pumpcavity with the central axis of said elongated accumulator chamber beingarranged parallel to said drive axis.
 9. The fuel pump assembly of claim8, wherein said accumulator housing has an axial extent which issubstantially greater than the axial extent of said pump housing therebycreating an axial overhang of said accumulator housing relative to saidpump housing.
 10. The fuel pump assembly of claim 9, wherein said pumphousing contains at least one additional pump cavity having a secondpump axis parallel to said first pump axis and perpendicular to saiddrive axis and further including a second pump plunger mounted forreciprocatory motion along said second pump axis in response torotational movement of said drive shaft.
 11. The fuel pump assembly ofclaim 10, further including a fuel distributor means for providingsequential periodic fluidic communication between said accumulatorchamber and the engine cylinders, said fuel distributor means includinga distributor housing mounted on said pump housing adjacent said driveshaft cavity in spaced apart generally parallel relationship with saidaxial overhang of said accumulator housing.
 12. The fuel pump assemblyof claim 11, wherein said distributor housing contains a rotor bore andsaid distributor means further includes a distributor rotor mounted forrotation within said rotor bore, said rotor being rotationally driven bysaid drive shaft, said rotor containing an axial supply passagefluidically connected to receive fuel from said accumulator chamber,said rotor also containing a first radial supply passage fluidicallyconnected to said axial supply passage, said distributor housingcontaining a set of receiving ports adapted to communicate withcorresponding engine cylinders through corresponding fuel injectionlines, said receiving ports being circumferentially spaced around saidrotor, said set of receiving ports being arranged in positions toregister successively with said first radial supply passage as saidrotor is rotated to define separate distinct periods during eachrotation of said rotor in which said corresponding engine cylinders maybe fluidically connected to said accumulator chamber.
 13. The fuel pumpassembly of claim 12, wherein the rotational axis of said rotor isco-axial with the rotational axis of said drive shaft.
 14. The fuel pumpassembly of claim 12, wherein the rotational axis of said rotor isperpendicular to the rotational axis of said drive shaft.
 15. The fuelpump assembly of claim 12, further including a fuel feed line forfluidically connecting said axial supply passage to said accumulatorchamber, said feed line including a feed port for supplying fuel fromsaid accumulator to said rotor bore, said feed port being located in asupply plane which is perpendicular to the rotational axis of said rotorand is axially spaced from said set of receiving ports, said rotorcontaining a radial receiving passage axially positioned within saidsupply plane.
 16. The fuel pump assembly of claim 15, wherein saiddistributor housing contains a distributor housing drain port located atone end of said rotor bore for communication with a low pressure fueldrain, said rotor contains a first axial drain passage fluidicallyconnected to said distributor housing drain port.
 17. The fuel pumpassembly of claim 16, wherein said rotor further contains a first radialdrain passage communicating with an axial drain passage and to a firstdrain groove formed in one of said rotor and said rotor bore locatedaxially between said first radial supply passage and said radialreceiving passage to receive any fuel which leaks through the closefitting clearance between said rotor and rotor cavity extending betweensaid radial supply passage and said radial receiving passage.
 18. Thefuel pump assembly of claim 16, further including a boost pump meanslocated between said distributor means and said pump housing forreceiving fuel from a fuel source and for supplying fuel to said pumpcavity at a pressure sufficient to provide an adequate amount of fuel tosaid pump cavity throughout the operating range of the engine.
 19. Thefuel assembly of claim 18, wherein said boost pump means includes ashaft extension coupled to said drive shaft of said fuel pump at one endand to said rotor distributor rotor at the other end, said distributorhousing having a seal recess surrounding the end of said distributorrotor adjacent said shaft extension.
 20. The fuel pump assembly of claim12, wherein said rotor contains a pressure equalizing groove extending asufficient circumferential distance around said rotor at an axiallocation to connect fluidically all said receiving ports except for thereceiving port which is in fluidic communication with said first radialsupply passage.
 21. The fuel pump assembly of claim 20, wherein saidreceiving ports are circumferentially spaced equal angularly around saidrotor to maximize the space between said receiving ports.
 22. The fuelpump assembly of claim 21, wherein said distributor means includes asupply groove contained in one of said rotor and said rotor bore, saidsupply groove being positioned to communicate at all times with saidradial receiving passage of said rotor and said fuel feed line.
 23. Thefuel pump assembly of claim 15, wherein said distributor means includesan injection control means for controlling the timing and quantity offuel injected into each engine cylinder in response to engine operatingconditions, said injection control means including a first solenoidinjection control valve mounted on said distributor housing and arrangedto control the flow of fuel through said fuel feed line, said firstsolenoid injection control valve being a three way valve operable whenenergized to connect said axial supply passage of said rotor with saidaccumulator and operable when de-energized to connect said axial supplypassage of said rotor bore with a low pressure drain wherein saiddistributor housing includes an elongated first valve cavity forreceiving said first solenoid injection control valve.
 24. The fuel pumpassembly of claim 23, wherein said injection control means includes asecond solenoid injection control valve mounted on said distributorhousing and arranged to control the flow of fuel through said fuel feedline in parallel with said first solenoid injection control valve, saidsecond solenoid injection control valve being a three way valve operablewhen energized to connect said axial supply passage of said rotor withsaid accumulator and operable when de-energized to connect said axialsupply passage of said rotor with a low pressure fuel drain, saiddistributor housing containing a second valve cavity having a centralaxis parallel to a central axis of said first valve cavity, said centralaxes residing within said supply plane containing said radial supplypassage supplying fuel to said axial supply passage of said rotor, saidfirst and second cavities being positioned on opposite sides of saidrotor.
 25. The fuel pump assembly of claim 24, wherein said first andsecond valve cavities interconnected by a rotor feed bore having acentral axis located in said supply plane, said feed port for said rotorcavity being fluidically connected with said rotor feed bore, saiddistributor means including a two way check valve located within saidrotor feed bore to prevent fuel supplied from one said valve cavity toflow into the other said valve cavity.
 26. An ultra high pressure fuelpump assembly for supplying fuel through plural fuel injection lines tothe corresponding cylinders of a multi-cylinder internal combustionengine having a predetermined operating range and having reciprocatingpistons associated with the respective cylinders, comprising:pump meansfor supplying fuel at a pressure above a predetermined operatingpressure; a high pressure accumulator means fluidically connected withsaid pump means for accumulating a predetermined volume of fuel at saidpredetermined operating pressure; a fuel distribution means forproviding sequential periodic fluidic communication between saidaccumulator means and the engine cylinders through the fuel injectionlines associated with the corresponding engine cylinders for causingperiodic injection of fuel into the corresponding engine cylinder intimed synchronism with the movement of the piston in the correspondingengine cylinder; wherein said high pressure accumulator means includes ahigh strength, compact accumulator housing containing a fluidicallyinterconnected labyrinth of accumulator chambers having a total volumesufficient to allow controlled quantities of fuel at the said operatingpressure to be delivered to each engine cylinder at appropriate timesthroughout the entire operating range of the engine as determined bysaid fuel distribution means.
 27. The fuel pump assembly of claim 26,wherein said pump means includes at least one pump unit for respondingto a control signal to vary the amount of fuel pumped, and furtherincluding pressure sensing means for determining the pressure withinsaid accumulator chambers and a pump control means for generating saidpump control signal to maintain the pressure of fuel in said accumulatorchambers at the predetermined operating pressure.
 28. The fuel pumpassembly of claim 26, wherein said accumulator chambers are elongatedand cylindrical in shape and are connected by connecting passages. 29.The fuel pump assembly of claim 28, wherein said accumulator chambersare positioned adjacent, and oriented in generally parallelrelationship, to each other.
 30. The fuel pump assembly of claim 28,wherein said accumulator chambers are positioned to intersect a verticalplane through said accumulator housing in a two dimensional array. 31.The fuel pump assembly to claim 30, wherein said two dimensional arrayincludes an upper row of four accumulator chambers and a lower row ofthree accumulator chambers.
 32. The fuel pump assembly of claim 28,wherein said accumulator housing is formed from an integral one pieceblock and wherein said accumulator means includes a plurality of plugslocated at the ends of respective accumulator chambers to sealfluidically the ends of said accumulator chambers.
 33. The fuel pumpassembly of claim 32, wherein said pump means includes a pump housingcontaining plural pump cavities and said accumulator housing is mountedon said pump housing and includes plural pump unit recesses aligned withand communicating with said pump cavities, respectively, and whereinsaid pump means includes plural pump units, each said pump unit beingmounted within a corresponding pump cavity and associated pump unitrecess.
 34. The fuel pump assembly of claim 33, wherein each said pumpunit includes a pump barrel containing a pump chamber and a pump plungermounted for reciprocal movement in said pump chamber.
 35. The fuel pumpassembly of claim 34, wherein said pump means includes a camshaftrotationally mounted within said pump housing, said camshaft includesplural cams for causing said plungers, respectively, to reciprocate assaid camshaft is rotated.
 36. The fuel pump assembly of claim 35,wherein said pump means includes a plurality of tappet assembliesassociated with said pump units, respectively, each said tappet assemblybeing mounted for reciprocal movement within the pump cavity in whichsaid corresponding pump unit is mounted and being connected with thepump plunger of the corresponding pump unit, and wherein said pump meansincludes a tappet bias spring for biasing said tappet assembly intoengagement with a corresponding cam on said camshaft to cause saidtappet assembly and the connected pump plunger to reciprocate as saidcamshaft is rotated.
 37. The fuel pump assembly of claim 35, whereineach said cam has at least one lobe for causing an associated pumpplunger to undergo one advancing stroke and one return stroke for eachrevolution of said camshaft, the total number of lobes on all said camsbeing selected to cause one advancing stroke for each of said periodicinjections into each of the engine cylinder.
 38. The fuel pump assemblyof claim 34, wherein each said pump unit includes a pump retainersurrounding said barrel, for supportively mounting the pump unit withinthe corresponding pump unit recess of said accumulator housing, eachsaid pump unit extending into the corresponding pump cavity withoutdirectly contacting said pump housing.
 39. The fuel pump assembly ofclaim 38, wherein each said pump unit contains a pump unit inletcommunicating with a source of fuel for feeding fuel into said pumpchamber and a pump unit outlet communicating with said labyrinth ofaccumulator chambers and wherein each said pump unit includes a pumpunit check valve for permitting only one way flow of fuel from the pumpchamber through said pump unit outlet into said accumulator chambers.40. The fuel pump assembly of claim 39, wherein each said pump unitcheck valve includes a check valve recess contained in said accumulatorhousing to form a fluid communication path between a corresponding diskoutlet passage and said accumulator chambers, each said pump unit checkvalve further including a check valve element adapted to be biased intoa closed position by the pressure of fuel within said accumulatorchambers until the pressure of fuel within the corresponding pumpchamber exceeds the pressure within said accumulator chambers at whichtime said check valve element is caused to open to allow fuel to flowfrom the corresponding pump chamber and through said check valve recessinto said accumulator chambers.
 41. The fuel pump assembly of claim 39,wherein each said pump unit includes a disk positioned within saidretainer at one end of said barrel to close off the corresponding pumpchamber, said pump unit disk containing said pump unit inlet and saidpump unit outlet and wherein said retainer is threadedly received withinthe corresponding pump unit recess of said accumulator housing to biassaid barrel and said disk in axially stacked relationship against saidaccumulator housing, said pump unit outlet including a disk outletpassage positioned centrally in said disk, said pump unit inletincluding an annular disk groove positioned concentrically on one sideof said disk and at least one axial disk inlet passage extending fromsaid pump chamber to said annular disk groove.
 42. The fuel pumpassembly of claim 41, wherein said accumulator housing contains at leastone common fuel feed passage for supplying fuel to all of said pumpunits and a plurality of fuel feed branches extending between saidcommon fuel feed passage and said pump unit recesses respectively, eachsaid fuel feed branch communicating at one end with said annular diskgroove contained in the corresponding pump unit recess and communicatingat the other end with said common fuel feed passage.
 43. The fuel pumpassembly of claim 42, further including a plurality of pump unit controlvalves associated with said fuel feed branches, respectively, to controlthe flow of fuel through the corresponding fuel feed branches inresponse to a pump unit control signal to control the amount of fuelpumped into said accumulator chambers by the corresponding pump unitduring each reciprocal cycle of the corresponding pump plunger.
 44. Thefuel pump assembly of claim 43, further including pressure sensing meansfor determining the pressure within said accumulator chambers and a pumpunit valve control means for generating said pump unit control signalfor each said pump unit control valve to maintain the pressure of fuelin said accumulator chambers at the predetermined operating pressure.45. The fuel pump assembly of claim 44, wherein said accumulator housingcontains an accumulator drain passage communicating with each said pumpunit recess and with said common fuel feed passage, each said pump unitincludes a pump unit drain means for directing fuel leaked from saidpump unit into said accumulator drain passage, each said pump unit drainmeans further including a recess clearance formed between thecorresponding retainer and the corresponding pump unit recess, each saidrecess clearance communicating with the corresponding accumulator drainpassage.
 46. The fuel pump assembly of claim 45, wherein each said drainmeans further includes a pump unit clearance between the correspondingbarrel and retainer, a drain groove located on the surface of thecorresponding pump plunger and a retainer drain passage communicating atall times with said pump unit clearance and communicating intermittentlywith said drain groove during reciprocal movement of the correspondingpump plunger, whereby fuel leaked from the corresponding pump chamberbetween the corresponding barrel and pump plunger will collect in saiddrain groove for intermittent drainage through the corresponding drainpassage.
 47. The fuel pump assembly of claim 46, wherein each said pumpunit clearance is fluidically connected to receive fuel leaked from thearea of contact between the corresponding disk and retainer and whereineach said recess clearance is fluidically connected to receive fuelleaked from the area of contact between the corresponding disk andaccumulator housing to allow fuel leaked from said contact areas to bereturned to said common fuel feed passage.
 48. The fuel pump assembly ofclaim 46, wherein each said pump unit check valve includes a check valverecess contained in said accumulator housing to form a fluidcommunication path between a corresponding disk outlet passage and saidaccumulator chambers, each said pump unit check valve further includinga check valve element adapted to be biased into a closed position by thepressure of fuel within said accumulator chambers until the pressure offuel within the corresponding pump chamber exceeds the pressure withinsaid accumulator chambers at which time said check valve element iscaused to open to allow fuel to flow from the corresponding pump chamberthrough said corresponding disk outlet passage and said check valverecess into said accumulator chambers.
 49. A fuel pump assembly forsupplying fuel to a multi-cylinder internal combustion engine above apredetermined high pressure, comprisinga compact pump housing havingminimal dimensions in mutually perpendicular lateral, radial and axialdirections, said pump housing containing at least one pump cavity havinga first pump axis extending in the radial direction; pumping meansmounted within said pump cavity for pressurizing fuel above thepredetermined high pressure; an accumulator housing containing at leastone accumulator chamber for accumulating and temporarily storing fuel athigh pressure, said accumulator housing being mounted on said pumphousing adjacent one end of said pump chamber, at least one of saidaxial extent and said lateral extent of said accumulator housing beinggreater than the corresponding extent of said pump housing therebycreating a cantilevered overhang of said accumulator housing relative tosaid pump housing; and pump control valve means connected with saidoverhang of said accumulator housing adjacent said pump housing forcontrolling the amount of fuel pumped into said accumulator chamber. 50.The fuel pump assembly of claim 49, wherein said pump housing includesplural pump cavities, said pumping means includes means for pressurizingfuel in all said pumping cavities for delivery to said accumulatorchamber.
 51. The fuel pump assembly of claim 50, wherein saidaccumulator housing contains at least one common fuel feed passage forsupplying fuel to all of said pump cavities and a plurality of fuel feedbranches extending between said common fuel feed passage and said pumpcavities, respectively, each said fuel feed branch communicating at oneend with a corresponding said pump cavity and communicating at the otherend with said common fuel feed passage.
 52. The fuel pump assembly ofclaim 51, wherein said pump control valve means includes a plurality ofpump control valves associated with said fuel feed branches,respectively, to control the flow of fuel through the corresponding fuelfeed branches in response to a pump control signal to control the amountof fuel pumped into said accumulator chambers by said pump means, saidpump control valves being mounted on said cantilevered overhang of saidaccumulator.
 53. The fuel pump assembly of claim 52, wherein said pumpcontrol valves are mounted in said cantilevered overhang in a positionimmediately adjacent said pump housing.
 54. The fuel pump assembly ofclaim 53, wherein cantilevered overhang extends in the lateral directionand said pump control valves are positioned along the lateral side ofsaid pump housing.
 55. The fuel pump assembly of claim 54, furtherincluding pressure sensing means for determining the pressure withinsaid accumulator chamber and wherein said cantilevered overhang of saidaccumulator also extends in the axial direction, said pressure sensingmeans being mounted in said axial portion of said cantilevered overhang.56. The fuel pump assembly of claim 55, wherein said pressure sensingmeans is mounted on the same side of said accumulator housing as saidpump housing.
 57. A high pressure fuel pump assembly for supplying fuelto an internal combustion engine, comprising:pump means for supplyingfuel above approximately 5,000 psi, said pump means including a pumphousing containing at least one pump cavity opening into a head engagingsurface; and a high pressure accumulator means fluidically connectedwith said pump means for accumulating a predetermined volume of fuel ata predetermined operating pressure above approximately 5,000 psi, saidhigh pressure accumulator means includes a high strength, compactaccumulator housing containing at least one accumulator chamber andmounted in contact with said head engaging surface of said pump housingto form an end wall for said pump cavity, wherein said accumulatorhousing includes a fluidically interconnected labyrinth of accumulatorchambers having a total volume sufficient to allow controlled quantitiesof fuel at the operating pressure to be delivered to the internalcombustion engine at appropriate times throughout the entire operatingrange of the engine.
 58. A high pressure fuel pump assembly as definedin claim 57, wherein said pump means is adapted to supply fuel at apressure above approximately 16,000 psi and said accumulator means isadapted to contain fuel at a pressure above approximately 16,000 psi.59. A high pressure fuel pump assembly as defined in claim 57, whereinsaid pump means is adapted to supply fuel at a pressure aboveapproximately 20,000 psi and said accumulator means is adapted tocontain fuel at a pressure above approximately 20,000 psi.
 60. A highpressure fuel pump assembly as defined in claim 57, wherein saidaccumulator housing is formed from material selected from the groupconsisting of SAE 4340 or Aermet
 100. 61. A high pressure fuel pumpassembly as defined in claim 57, wherein said accumulator housing isformed of an integral one piece block containing said labyrinth ofaccumulator chambers shaped and positioned to form surrounding wallssufficiently strong to withstand the forces generated when saidaccumulator chambers are filled with fuel at the predetermined operatingpressure.
 62. A high pressure fuel pump assembly as defined in claim 61,wherein said accumulator chambers are formed by boring said one pieceblock, and wherein said accumulator includes a plurality of separateplugs for sealing said accumulator chambers respectively.
 63. A highpressure fuel pump assembly as defined in claim 62, wherein theaggregate volume of said accumulator chambers is sufficient to limit thedrop in fuel pressure within said accumulator throughout the entireoperating range of the engine to no more than approximately 5%-10% ofsaid predetermined operating pressure.
 64. A high pressure fuel pumpassembly as defined in claim 63, wherein said accumulator block wallsare sufficiently strong to allow said accumulator chambers to hold fuelat a predetermined pressure above 5,000 psi.
 65. A high pressure fuelpump assembly as defined in claim 64, wherein said accumulator blockwalls are sufficiently strong to allow said accumulator chambers to holdfuel at a predetermined pressure above 20,000 psi.
 66. A high pressurefuel pump assembly as defined in claim 65, wherein said accumulatorchambers are elongated and cylindrical in shape and are connected byconnecting passages.
 67. A high pressure fuel pump assembly as definedin claim 66, wherein said accumulator chambers are positioned adjacent,and oriented in generally parallel relationship, to each other.
 68. Ahigh pressure fuel pump assembly as defined in claim 67, wherein saidaccumulator chambers are positioned to intersect a vertical planethrough said accumulator housing in a two dimensional array.
 69. A highpressure fuel pump assembly as defined in claim 68, wherein saidaccumulator chambers are fluidically interconnected by a first crosspassage which intersects an upper row of accumulator chambers and asecond cross passage which intersects a lower row of accumulatorchambers.
 70. A high pressure fuel pump assembly as defined in claim 69,wherein said two dimensional array includes an upper row of fouraccumulator chambers and a lower row of three accumulator chambers. 71.A high pressure fuel pump assembly as defined in claim 70, whereinaccumulator means includes a plurality of plugs located at the ends ofrespective accumulator chambers to seal fluidically the ends of saidaccumulator chambers.
 72. A high pressure fuel pump assembly forperiodic injection of fuel through plural fuel injection lines intocorresponding engine cylinders of a plural cylinder internal combustionengine having a predetermined operating range and a plurality ofreciprocating pistons associated with the corresponding cylinders,comprising:a compact pump housing having minimal dimensions in mutuallyperpendicular lateral, radial and axial directions, said pump housingcontaining at least one pump cavity having a first central axisextending in the radial direction; a pump plunger mounted within saidpump cavity for reciprocatory motion along said first central axis; anaccumulator housing containing at least one accumulator chamber foraccumulating and temporarily storing fuel at high pressure, saidaccumulator housing being mounted on said pump housing adjacent one endof said pump chamber, at least one of said axial extent and said lateralextent of said accumulator housing being greater than the correspondingextent of said pump housing thereby creating a cantilevered overhang ofsaid accumulator housing relative to said pump housing; and a fueldistributor means for providing sequential periodic fluidiccommunication between said accumulator means and the engine cylindersthrough the corresponding fuel injection lines associated with thecorresponding engine cylinders for causing periodic injection of fuelinto the corresponding engine cylinder in timed synchronism with themovement of the pistons in the corresponding cylinders, said fueldistribution means including a distributor body cantilever mounted onsaid pump housing in parallel, generally spaced apart relationship withrespect to said overhang of said accumulator housing.
 73. A highpressure fuel pump assembly as defined in claim 72, wherein saiddistributor means includes an injection control means for controllingthe timing and quantity of fuel injected into each engine cylinder inresponse to engine operating conditions, said first control meansincluding a first solenoid injection control valve mounted on saiddistributor housing and arranged to control the flow of fuel in saidfuel injection lines, said first solenoid injection control valve beingmounted on said distributor housing in the space between saiddistributor housing and said cantilevered overhang of said accumulatorhousing.
 74. A high pressure fuel pump assembly as defined in claim 73,wherein said injection control means includes a second solenoidinjection control valve for controlling the flow of fuel from saidaccumulator to said respective engine cylinders, said second solenoidinjection control valve being mounted on said distributor housingadjacent said first solenoid injection control valve in the spacebetween said distributor housing and said cantilevered overhang of saidaccumulator housing.
 75. A high pressure fuel pump assembly as definedin claim 74, wherein said first and second solenoid injection controlvalves are three way valves operable when energized to connect one ofthe fuel injection lines with said accumulator and operable whende-energized to connect one of the fuel injection lines with a lowpressure fuel drain.
 76. A high pressure fuel pump assembly as definedin claim 73, wherein said first solenoid injection control valve is athree way valve operable when energized to connect one of the fuelinjection lines with said accumulator and operable when de-energized toconnect one of the fuel injection lines with a low pressure fuel drain.77. A fuel pump assembly for supplying fuel at pressures above apredetermined high pressure to an internal combustion engine having anirregular transverse profile, comprisinga compact pump housing havingminimal dimensions in mutually perpendicular lateral and radialdirections, said pump housing containing at least one pump cavity havinga first pump axis extending in the radial direction; pumping meansmounted within said pump cavity for pressurizing fuel above thepredetermined high pressure; an accumulator housing containing at leastone accumulator chamber for accumulating and temporarily storing fuel athigh pressure, said accumulator housing being mounted on said pumphousing adjacent one end of said pump cavity, said lateral extent ofsaid accumulator housing being greater than the lateral extent of saidpump housing thereby a cantilevered lateral overhang of said accumulatorhousing relative to said pump housing to form an offset transverseprofile which allows the fuel pump assembly to be mounted on theinternal combustion engine at a location wherein the transverse profileof the fuel pump assembly complements the irregular transverse profileof the internal combustion engine.
 78. The fuel pump assembly of claim77, further including pump control valve means connected with saidlateral overhang of said accumulator housing adjacent said pump housingfor controlling the amount of fuel pumped into said accumulator chamberin response to a pump control signal.
 79. The fuel pump assembly ofclaim 78, wherein said pump housing includes plural pump cavities, saidpumping means includes plural pump units corresponding to the number ofsaid pump cavities and located in said pump cavities, respectively, eachsaid pump unit operating to pressurize fuel for delivery to saidaccumulator chamber.
 80. The fuel pump assembly of claim 79, whereinsaid accumulator housing contains at least one common fuel feed passagefor supplying fuel to all of said pump cavities and a plurality of fuelfeed branches extending between said common fuel feed passage and saidpump cavities, respectively, each said fuel feed branch communicating atone end with a corresponding said pump cavity and communicating at theother end with said common fuel feed passage.
 81. The fuel pump assemblyof claim 80, wherein said pump control valve means includes a pluralityof pump control valves associated with said fuel feed branches,respectively, to control the flow of fuel through the corresponding fuelfeed branches in response to a pump control signal to control the amountof fuel pumped into said accumulator chambers by said pump means, saidpump control valves being mounted on said lateral overhang of saidaccumulator.
 82. A fuel pump assembly, comprisinga pump housingcontaining an outwardly opening pump cavity, a drive shaft rotatablymounted in the pump housing, a pump head mountable on the pump housingto close the outwardly opening pump cavity, said pump head containing apump unit recess positioned to communicate with the pump cavity, and areplaceable pump unit including a pump barrel containing a pump chamberand a pump plunger adapted to be mounted for reciprocal movement withinsaid pump chamber in response to rotation of said drive shaft, saidreplaceable pump unit including retaining means for mounting said pumpunit within said pump unit recess of said pump head in a position toextend at least partially into said pump cavity in spaced apartnon-contacting relationship with said pump housing.
 83. The fuel pumpassembly of claim 82, wherein said pump housing includes a plurality ofsaid outwardly opening pump cavities, said pump head containing aplurality of said pump unit recesses positioned to communicate with saidpump cavities, respectively, and further including a plurality of saidreplaceable pump units, each said pump unit including a pump barrelcontaining a pump chamber, a pump plunger mounted for reciprocationwithin said pump chamber when said drive shaft rotates and a retainingmeans for mounting said pump unit within a corresponding said pump unitrecess of said pump head in a position to extend at least partially intosaid pump cavity in spaced apart non-contacting relationship with saidpump housing.
 84. The fuel pump assembly of claim 83, wherein said driveshaft includes a plurality of cams for causing said pump plungers toreciprocate, and further including a plurality of tappet assembliesassociated with said pump units, respectively, each said tappet assemblybeing mounted for reciprocal movement within a corresponding pump cavityand being connected with a corresponding pump plunger, and a pluralityof tappet bias springs for biasing said tappet assemblies intoengagement with said cams, respectively, to cause said tappet assembliesand the connected pump plungers to reciprocate as said drive shaft isrotated.
 85. The fuel pump assembly of claim 84, wherein said pumphousing is an integral single piece structure including a head engagingsurface for precisely positioning said pump head and tappet guidingsurfaces within said pump cavities for guiding said tappets,respectively, said pump housing further including a radially encloseddrive shaft cavity having substantial radial openings only through saidpump cavities, said pump housing including drive shaft support surfacesfor precisely supporting said drive shaft, said pump housing requiringclose tolerance machining of only said head engaging surface, saidtappet guiding surfaces and said drive shaft support surfaces to providesuitable alignment of said pump chambers with respect to said tappetsand said drive shaft.
 86. The fuel pump assembly of claim 85, whereinsaid pump housing is formed by metal casting procedures.
 87. Anaccumulator for use in a high pressure fuel system for temporarilystoring fuel at a predetermined operating pressure to supply fuel forperiodic injection into the corresponding engine cylinder of a pluralcylinder internal combustion engine having a predetermined operatingrange and a plurality of engine pistons mounted for reciprocal movementwithin the engine cylinders, comprisinga high strength, compactaccumulator housing containing a fluidically interconnected labyrinth ofaccumulator chambers whose aggregate volume is sufficient to allow acontrolled quantity of fuel at the predetermined operating pressure tobe delivered to each engine cylinder at appropriate times throughout theentire operating range of the engine, said accumulator housing beingformed of an integral one piece block containing said labyrinth ofaccumulator chambers shaped and positioned to form surrounding wallssufficiently strong to withstand the forces generated when saidaccumulator chambers are filled with fuel at the predetermined operatingpressure, said accumulator chambers being positioned to intersect avertical plane through said accumulator housing in at least a twodimensional array.
 88. The accumulator as defined in claim 87, whereinsaid accumulator chambers are formed by boring said one piece block, andwherein said accumulator includes a plurality of separate plugs forsealing said accumulator chambers respectively.
 89. The accumulator asdefined by claim 88, wherein the aggregate volume of said accumulatorchambers is sufficient to limit the drop in fuel pressure within saidaccumulator throughout the entire operating range of the engine to nomore than approximately 5%-10% of said predetermined operating pressure.90. The accumulator of claim 87, wherein said accumulator block wallsare sufficiently strong to allow said accumulator chambers to hold fuelat a predetermined pressure above 5,000 psi.
 91. The accumulator ofclaim 90, wherein said accumulator block walls are sufficiently strongto allow said accumulator chambers to hold fuel at a predeterminedpressure above 20,000 psi.
 92. The accumulator of claim 90, wherein saidaccumulator chambers are elongated and cylindrical in shape and areconnected by connecting passages.
 93. The accumulator of claim 92,wherein said accumulator chambers are positioned adjacent, and orientedin generally parallel relationship, to each other.
 94. The accumulatorof claim 93, wherein said two dimensional array includes an upper row ofa plurality of said accumulator chambers and a lower row of a pluralityof said accumulator chambers.
 95. The accumulator of claim 94, whereinsaid accumulator chambers are fluidically interconnected by a firstcross passage which intersects an upper row of accumulator chambers anda second cross passage which intersects a lower row of accumulatorchambers.
 96. The accumulator of claim 95, wherein said upper rowincludes four accumulator chambers and said lower row includes threeaccumulator chambers.
 97. The accumulator of claim 96, whereinaccumulator means includes a plurality of plugs located at the ends ofrespective accumulator chambers to seal fluidically the ends of saidaccumulator chambers.
 98. The accumulator of claim 104, adapted to bemounted on a pump housing of a fuel pump which is adapted to supply fuelabove said predetermined operating pressure, wherein said accumulatorhousing includes plural pump recesses, said accumulator furtherincluding plural pump units received in said pump recesses,respectively, and supported by said accumulator housing, each said pumpunit recess being fluidically connected with said accumulator chambers.99. The accumulator of claim 98, wherein said accumulator housingcontains at least one common fuel feed passage for supplying fuel to allof said pump units and a plurality of fuel feed branches extendingbetween said common fuel feed passage and said pump unit recesses,respectively, each said fuel feed branch communicating at one end withsaid corresponding pump unit recess and communicating at the other endwith said common fuel feed passage.
 100. The accumulator of claim 99,further including a plurality of pump unit control valves associatedwith said fuel feed branches, respectively, to control the flow of fuelthrough the corresponding fuel feed branches in response to a pump unitcontrol signal to control the amount of fuel pumped into saidaccumulator means by the corresponding pump unit.
 101. The accumulatorof claim 98, further including pressure sensing means for determiningthe pressure within said accumulator chambers and a pump unit valvecontrol means for generating said pump unit control signal for each saidpump unit control valve to maintain the pressure of fuel in saidaccumulator chambers at the predetermined operating pressure.
 102. Theaccumulator of claim 100, wherein said accumulator housing contains anaccumulator drain passage communicating with each said pump unit recessand with said common fuel feed passage, each said pump unit includes apump unit drain means for directing fuel leaked from said pump unit intosaid accumulator drain passage, each said pump unit drain means furtherincluding a recess clearance formed between the corresponding said pumpunit and the corresponding pump unit recess, each said recess clearancecommunicating with the corresponding accumulator drain passage.
 103. Theaccumulator of claim 101, wherein each said pump unit includes a checkvalve to permit only one way flow of fuel from said pump unit into saidaccumulator chambers, each said pump unit check valve further includinga check valve element adapted to be biased into a closed position by thepressure of fuel within said accumulator chambers until the pressure offuel within the corresponding pump chamber exceeds the pressure withinsaid accumulator chambers at which time said check valve element iscaused to open to allow fuel to flow from the corresponding pump chamberinto said accumulator chambers.
 104. The accumulator of claim 98,wherein said accumulator housing further contains a plurality of checkvalve recesses associated with said pump unit recesses, respectively,for forming a fluidic passage between said pump unit recesses and saidaccumulator chambers, each said check valve recess being adapted toreceive a check valve for permitting only one way flow of fuel from thecorresponding pump unit into said accumulator chambers.
 105. Theaccumulator of claim 100, wherein said accumulator housing furtherincludes a plurality of control valve recesses within which the pumpunit control valves are adapted to be mounted.
 106. The accumulator ofclaim 105, wherein the central axis of said pump control valve recessesare parallel and are oriented to intersect an extension of the centralaxis of one of said accumulator chambers.
 107. The accumulator of claim105, wherein said upper row of accumulator chambers extend alongsubstantially the entire length of said accumulator housing and saidlower row of accumulator chambers are substantially shorter than theentire length of said accumulator, said pump unit recesses beingpositioned in alignment with an extension of the central axis of one ofsaid accumulator chambers forming said lower row.
 108. The accumulatorof claim 107, further including pressure sensing means for determiningthe pressure within said accumulator chambers and a pump unit valvecontrol means for generating said pump unit control signal for each saidpump unit control valve to maintain the pressure of fuel in saidaccumulator chambers at the predetermined operating pressure.
 109. Theaccumulator of claim 108, wherein said accumulator housing contains anaccumulator drain passage communicating with each said pump unit recessand with said common fuel feed passage to receive fuel leaked from thepump unit into said pump unit recess for return back to said common fuelfeed passage.
 110. An accumulator for use in a high pressure fuel systemfor temporarily storing fuel at a predetermined operating pressure tosupply fuel for periodic injection into the corresponding enginecylinder of a plural cylinder internal combustion engine having apredetermined operating range and a plurality of engine pistons mountedfor reciprocal movement within the engine cylinders, comprisinga highstrength, compact accumulator housing containing a fluidicallyinterconnected labyrinth of accumulator chambers whose aggregate volumeis sufficient to allow a controlled quantity of fuel at thepredetermined operating pressure to be delivered to each engine cylinderat appropriate times throughout the entire operating range of theengine, said accumulator housing being formed of an integral one pieceblock containing said labyrinth of accumulator chambers shaped andpositioned to form surrounding walls sufficiently strong to withstandthe forces generated when said accumulator chambers are filled with fuelat the predetermined operating pressurewherein said accumulator isformed from SAE 4340 or Aermet
 100. 111. A unitized fuel pump assemblyfor sequential periodic injection of fuel through plural fuel injectionlines into corresponding engine cylinders of a plural cylinder internalcombustion engine having a predetermined operating range and a pluralityof reciprocating pistons associated with the corresponding cylinders,comprising:pump means for pressurizing fuel, said pump means including apump housing and a drive shaft mounted within said housing for rotationabout a rotational axis, said pump housing containing a plurality ofpump cavities positioned along said rotational axis, said pump cavitiesbeing aligned along said rotational axis in a single radial direction;accumulator means for accumulating and temporarily storing fuel underpressure received from said pump means, said accumulator means includingan accumulator housing mounted on said pump housing in a position whichis separated from said drive shaft cavity by said pump cavities; a fueldistributor means for providing sequential periodic fluidiccommunication between said accumulator means and each of the enginecylinders through the corresponding fuel injection lines associated withthe corresponding engine cylinders for causing periodic injection offuel into the corresponding engine cylinder, said fuel distributionmeans including a distributor housing mounted on said pump housingadjacent one end of said drive shaft cavity, and injection control valvemeans for controlling the timing and quantity of fuel injected into eachcylinder in response to engine operating conditions, said injectioncontrol valve means including a solenoid operator mounted on saiddistributor housing oriented generally in the same radial direction assaid pump cavities relative to said rotational axis of said drive shaft.112. The fuel pump assembly of claim 111, wherein said distributorhousing includes a rotor bore and a set of receiving ports adapted tocommunicate with a corresponding set of fuel injection lines,respectively, said set of receiving ports opening into said rotor boreat circumferentially spaced apart locations within a distribution planeperpendicular to the central axis of said rotor bore, and wherein saiddistributor means includes a rotor adapted to be mounted for rotationwithin said rotor bore, said rotor containing an axial supply passagefluidically connected to receive fuel from said accumulator means, saidrotor also containing a radial supply passage located within saiddistribution plane and rotor drive connection means for connecting saidrotor to said pump drive shaft in a manner to cause said radial supplypassage to align sequentially and successively with said receiving portsto supply fuel periodically to the corresponding engine cylinders asnecessary for engine operation.
 113. The fuel pump assembly of claim112, further including a fuel feed line for fluidically connecting saidaxial supply passage to said accumulator means, said distributor housingcontaining a feed port for supplying fuel from said accumulator to saidrotor bore, said feed port being located in a supply plane which isperpendicular to the rotational axis of said rotor and is axially spacedfrom said distributor plane, said rotor containing a radial receivingpassage axially positioned within said supply plane and connected withsaid axial supply passage in said rotor.
 114. The fuel pump assembly ofclaim 113, wherein said distributor housing contains a distributorhousing drain port located at one end of said rotor bore forcommunication with a low pressure fuel drain, said rotor contains afirst axial drain passage fluidically connected to said distributorhousing drain port, said rotor further containing a first radial drainpassage communicating with said axial drain passage.
 115. The fuel pumpassembly of claim 114, wherein said rotor is coupled to said drive shaftat the end of said rotor opposite said distributor housing drain port,said distributor housing having a seal recess surrounding the end ofsaid rotor adjacent the drive shaft coupling, and wherein saiddistributor means further includes a fuel seal located within said sealrecess.
 116. The fuel pump assembly of claim 115, wherein said receivingports are circumferentially spaced equal angularly around said rotor tomaximize the space between said receiving ports.
 117. The fuel pumpassembly of claim 116, further including a supply groove contained inone of said rotor and said rotor bore, said supply groove beingpositioned in said supply plane to communicate at all times with saidradial receiving passage of said rotor and said fuel feed line.
 118. Thefuel pump assembly of claim 113, wherein said injection control valvemeans is arranged to control the flow of fuel through said fuel feedline, said first solenoid injection control valve being a three wayvalve operable when energized to connect said axial supply passage ofsaid rotor with said accumulator means and operable when de-energized toconnect said axial supply passage of said rotor with a low pressuredrain, wherein said distributor housing includes an elongated firstvalve cavity for receiving said first injection control valve.
 119. Thefuel pump assembly of claim 118, wherein said injection control valvemeans includes a second injection control valve mounted on saiddistributor housing and arranged to control the flow of fuel through thefuel feed line in parallel with said first injection control valve, saidsecond solenoid injection control valve being a three way valve operablewhen energized to connect said axial supply passage of said rotor withsaid accumulator means and operable when de-energized to connect saidaxial supply passage of said rotor with a low pressure fuel drain, saiddistributor housing contains a second valve cavity having a central axisparallel to the central axis of said first valve cavity, said centralaxes residing within said supply plane containing said radial supplypassage supplying fuel to said axial supply passage of said rotor, saidfirst and second valve cavities being positioned on opposite sides ofsaid rotor.
 120. The fuel pump assembly of claim 119, wherein said firstand second valve cavities are interconnected by a rotor feed bore havinga central axis located in said supply plane, said feed port for saidrotor cavity being fluidically connected with said rotor feed bore, saiddistributor means including a two way check valve located within saidrotor feed bore to prevent fuel supplied from one said three way valveinto said rotor feed bore to flow into the drain groove of the otherthree way valve.
 121. A unitized, single piece fuel pump housing for afuel pump assembly having a rotatable camshaft for causing a pluralityof pump plungers to reciprocate in response to the reciprocatingmovement of a plurality of camshaft engaging tappets, comprisinga pumphousing containing a plurality of outwardly opening pump cavities and aradially enclosed cam shaft cavity communicating with said pumpcavities, said cam shaft cavity adapted to receive a rotatable camshaft, a pump head engaging surface formed on said pump body forprecisely positioning a pump head to allow the outwardly opening pumpcavities to be closed when a pump head is mounted on said pump body, anda plurality of tappet guiding surfaces within said pump cavities forguiding the tappets, said head engaging surface and said tappet guidingsurfaces being machined to closer tolerances than the remainder of saidpump cavities.
 122. The fuel pump housing of claim 121, wherein saidpump body is formed by metal casting procedures.
 123. A high pressurefuel system for supplying fuel at a predetermined pressure throughplural fuel injection lines to the corresponding cylinders of amulti-cylinder internal combustion engine, comprising:a fuel supplymeans for supplying fuel for delivery to the internal combustion engine,said fuel supply means including a fuel transfer circuit; a pump meansfor pressurizing fuel above the predetermined pressure; an accumulatormeans for accumulating and temporarily storing fuel at high pressurereceived from said pump means; a fuel distributor means fluidicallyconnected with said accumulator means through said fuel transfer circuitfor enabling sequential periodic fluidic communication with the enginecylinders through the corresponding fuel injection lines; a solenoidoperated injection control valve positioned within said fuel transfercircuit between said accumulator means and said fuel distributor meansfor controlling the fuel injected into each engine cylinder during eachof the sequential periods of communication enabled by said fueldistributor means to thereby define sequential injection events, saidsolenoid operated injection control valve movable between an openposition permitting fuel flow from said accumulator means to said fueldistributor means and a closed position blocking fuel flow from saidaccumulator means to said fuel distributor means; and a rate shapingcontrol means positioned within said fuel transfer circuit between saidaccumulator means and said fuel distributor means for producing apredetermined time varying change in the pressure of fuel during eachinjection event occurring sequentially at each engine cylinder to effectinjection.
 124. The high pressure fuel system of claim 123, wherein saidrate shaping control means includes a flow limiting means positionedwithin said fuel transfer circuit between said accumulator means andsaid fuel distributor means for limiting the flow of fuel from saidaccumulator to said fuel distributor means during only a portion of eachof said sequential injection events.
 125. The high pressure fuel systemof claim 124, wherein said rate shaping control means further includes aby-pass passage for directing fuel flow around said flow limiting meansand a rate shaping by-pass valve positioned within said by-pass passage,said rate shaping by-pass valve movable into a closed position blockingfuel flow through said by-pass passage and an open position permittingflow through said by-pass passage.
 126. The high pressure fuel system ofclaim 125, wherein said flow limiting means includes a fixed orificehaving a constant cross-sectional flow area for restricting fuel flowthrough said fuel transfer circuit.
 127. The high pressure fuel systemof claim 125, wherein said flow limiting means includes a variable flowcontrol valve movable between a first position permitting fuel to flowthrough said fuel transfer circuit at a first flow rate and a secondposition permitting fuel to flow through said fuel transfer circuit at asecond flow rate.
 128. The high pressure fuel system of claim 127,wherein said first flow rate occurs during a first portion of each saidinjection event and said second flow rate occurs during a second portionof each said injection event following said first portion, said firstflow rate being greater than said second flow rate.
 129. The highpressure fuel system of claim 128, wherein movement of said rate shapingby-pass valve to said open position permits fuel to flow through saidfuel transfer circuit at a third flow rate, said third flow rate beinggreater than said second flow rate, said third flow rate occurringduring a third portion of each injection event following said secondportion.
 130. The high pressure fuel system of claim 128, wherein saidvariable flow control valve includes a slidable piston having first andsecond ends, a central bore having an inner end and an outer end, saidouter end opening to said first end of said slidable piston, saidslidable piston including a plurality of orifices extending from saidinner end of said central bore through said second end.
 131. The highpressure fuel system of claim 130, wherein said variable flow controlvalve includes a biasing spring operatively connected to said slidablepiston for biasing said slidable piston towards said first position.132. The high pressure fuel system of claim 131, wherein said slidablepiston is mounted within a cavity arranged to cause said slidable pistonto move towards said second position whenever the upstream pressureexceeds the downstream pressure by a predetermined amount.
 133. The highpressure fuel system of claim 123, wherein said rate shaping controlmeans permits fuel pressure in a respective fuel injection line adjacentthe respective engine cylinder to increase prior and during each saidinjection event at a first high rate followed by a low rate less thansaid first high rate followed by a second high rate.
 134. The highpressure fuel system of claim 123, wherein said rate shaping controlmeans includes a variable flow control valve movable between a firstposition effecting said first high pressure rate and a second positioneffecting said low pressure rate.
 135. The high pressure fuel system ofclaim 123, wherein fuel from said accumulator means is capable ofreaching a maximum unrestricted flow rate corresponding to a maximumpressure in each of said fuel injection lines adjacent the respectiveengine cylinder during said injection event, said fuel transfer circuitincluding a first passage extending between said accumulator means andsaid injection control valve, said injection rate control meansincluding said first passage, said first passage having a predeterminedlength sufficient to cause a predetermined time delay between themovement of said solenoid operated injection control valve to the openposition and the attainment of said maximum pressure.
 136. The highpressure fuel system of claim 135, wherein movement of said solenoidoperated injection control valve to said open position creates apressure wave in said fuel transfer circuit, the pressure wave travelingfrom said solenoid operated injection control valve to an enginecylinder to define a wave traveling time period, wherein saidpredetermined length of said first passage is selected to provide adesired wave traveling time period.
 137. The high pressure fuel systemof claim 135, wherein said injection rate control means further includesa second passage positioned in parallel to said first passage fordirecting flow from said accumulator means to said injection controlvalve, and an orifice positioned in said second passage.
 138. The highpressure fuel system of claim 137, wherein said rate shaping controlmeans permits fuel pressure in one of said fuel injection lines adjacenta respective engine cylinder to increase during each said injectionevent at a first high rate followed by a low rate less than said firsthigh rate followed by a second high rate, said orifice having aneffective cross sectional flow area for slowing said first high rate andsaid low rate to desired levels.
 139. The high pressure fuel system ofclaim 123, wherein said rate shaping control means is positioned withsaid fuel transfer circuit between said accumulator means and saidsolenoid operated injection control valve, further including acavitation control means for minimizing cavitation in said fuel transfercircuit between said cavitation control means and the cylinders, saidcavitation control means including a reverse flow restrictor valvepositioned within said fuel transfer circuit between said injectioncontrol valve and said fuel distributor means for allowing for at leasta predetermined time period substantially unimpeded forward flow of fueltoward each engine cylinder while substantially restricting reverseflow.
 140. The high pressure fuel system of claim 123, further includinga cavitation control means for minimizing cavitation in said fueltransfer circuit and the fuel injection lines between said injectioncontrol valve and the engine cylinders, said cavitation control meansoperable to maintain fuel in said fuel transfer circuit downstream ofsaid fuel distributor means, said cavitation control means including anauxiliary fuel supply connected to said drain passage for supplyingpressurized fuel at an auxiliary supply pressure to said fuel transfercircuit downstream of said injection control valve when said injectioncontrol valve is in said closed position, wherein said auxiliary supplypressure is high enough to minimize the effects of cavitation while lowenough to cause no fuel injection.
 141. The high pressure fuel system ofclaim 123, further including a drain passage for connection to said fueltransfer circuit, said injection control valve being operable to connectsaid fuel transfer circuit to said drain passage to define a drainingevent, further including a cavitation control means for minimizingcavitation in said fuel transfer circuit and the fuel injection linesbetween said injection control valve and the engine cylinders, saidcavitation control means including a pressure regulating meanspositioned in said drain passage for maintaining fuel in said fueltransfer circuit downstream of said injection control valve and in thefuel injection lines at a regulated pressure during said draining event.142. A high pressure fuel system for supplying fuel at a predeterminedpressure through plural fuel injection lines to the correspondingcylinders of a multi-cylinder internal combustion engine, comprising:afuel supply means for supplying fuel for delivery to the internalcombustion engine, said fuel supply means including a fuel transfercircuit; a pump means for pressurizing fuel above the predeterminedpressure, said pump means including plural pump chambers and plural pumpplungers mounted for reciprocal movement in said pump chambers; aconstant volume high pressure accumulator means for accumulating andtemporarily storing fuel at high pressure received from said pump means;a fuel distributor means fluidically connected with said constant volumehigh pressure accumulator means through said fuel transfer circuit forenabling sequential periodic fluidic communication with the enginecylinders through the corresponding fuel injection lines; an injectioncontrol valve means for controlling the fuel injected into each enginecylinder during each of the sequential periods of communication enabledby said fuel distributor means to thereby define sequential injectionevents; and a rate shaping control means positioned within said fueltransfer circuit between said constant volume high pressure accumulatormeans and said fuel distributor means for producing a predetermined timevarying change in the rate of fuel injected into each engine cylinderduring said sequential injection events.
 143. A high pressure fuelsystem for supplying fuel at a predetermined pressure through pluralfuel injection lines to the corresponding cylinders of a multi-cylinderinternal combustion engine, comprising:a fuel supply means for supplyingfuel for delivery to the internal combustion engine, said fuel supplymeans including a fuel transfer circuit; a pump means for pressurizingfuel from said fuel supply means above the predetermined pressure; afuel distributor means fluidically connected with said pump meansthrough said fuel transfer circuit for enabling sequential periodicfluidic communication with the engine cylinders through thecorresponding fuel injection lines; an injection control means forcontrolling the fuel injected into each engine cylinder during each ofthe sequential periods of communication enabled by said fuel distributormeans to thereby define sequential injection events; and a rate shapingcontrol means positioned within said fuel transfer circuit between saidpump means and said fuel distributor means for producing a predeterminedtime varying change in the rate of fuel injected into each enginecylinder during said sequential injection events, wherein said rateshaping control means includes a flow limiting means positioned withinsaid fuel transfer circuit between said pump means and said fueldistributor means for limiting the flow of fuel from said pump means tosaid fuel distributor means during each of said sequential injectionevents, a by-pass passage for directing fuel flow around said flowlimiting means and a rate shaping by-pass valve positioned within saidby-pass passage.
 144. The high pressure fuel system of claim 143,wherein said rate shaping by-pass valve is movable into a closedposition blocking fuel flow through said by-pass passage and an openposition permitting flow through said by-pass passage.
 145. The highpressure fuel system of claim 144, wherein said flow limiting meansincludes a fixed orifice having a constant cross-sectional flow area forrestricting fuel flow through said fuel transfer circuit.
 146. The highpressure fuel system of claim 144, wherein said flow limiting meansincludes a variable flow control valve movable between a first positionpermitting fuel to flow through said fuel transfer circuit at a firstflow rate and a second position permitting fuel to flow through saidfuel transfer circuit at a second flow rate.
 147. The high pressure fuelsystem of claim 144, further including an accumulator means positionedalong said fuel transfer circuit between said pump means and saidinjection control means for accumulating and temporarily storing fuel athigh pressure received from said pump means.
 148. The high pressure fuelsystem of claim 144, wherein said injection control means includes athree-way solenoid operated valve positioned along said fuel transfercircuit between said pump means and said distributor means, said rateshaping control means being positioned within said fuel transfer circuitbetween said three-way solenoid operated valve and said fuel distributormeans.
 149. A high pressure fuel system for supplying fuel at apredetermined pressure through plural fuel injection lines to thecorresponding cylinders of a multi-cylinder internal combustion engine,comprising:a fuel supply means for supplying fuel for delivery to theinternal combustion engine, said fuel supply means including a fueltransfer circuit; a pump means for pressurizing fuel above thepredetermined pressure; an accumulator means for accumulating andtemporarily storing fuel at high pressure received from said pump means;a fuel distributor means fluidically connected with said accumulatormeans through said fuel transfer circuit for enabling sequentialperiodic fluidic communication with the engine cylinders through thecorresponding fuel injection lines; an solenoid operated injectioncontrol valve positioned within said fuel transfer circuit between saidaccumulator means and said fuel distributor means for controlling thefuel injected into each engine cylinder during each sequential periodsof communication enabled by said fuel distributor means; a cavitationcontrol means for minimizing cavitation in said fuel transfer circuitbetween said cavitation control means and the cylinders, said cavitationcontrol means including a reverse flow restrictor valve positionedwithin said fuel transfer circuit between said injection control valveand said fuel distributor means for allowing substantially unimpededforward flow of fuel toward each engine cylinder while substantiallyrestricting reverse flow.
 150. The high pressure fuel system of claim149, further including a drain passage for connection to said fueltransfer circuit, wherein said solenoid operated injection control valveis movable between an open position allowing fuel flow from saidaccumulator means to said fuel distributor means and a closed positionblocking flow from said accumulator means while fluidically connectingsaid drain passage to said fuel transfer circuit downstream of saidsolenoid operated injection control valve, said reverse flow restrictorvalve being operable to permit substantially unrestricted fuel flow fromsaid solenoid operated injection control valve to said fuel distributorwhen said solenoid operated injection control valve is in said openposition and to restrict fuel flowing from said fuel distributor towardsaid solenoid operated injection control valve when said solenoidoperated injection control valve is in said closed position.
 151. Thehigh pressure fuel system of claim 150, wherein said fuel distributormeans includes a distributor housing and further including a injectioncontrol valve housing for housing said solenoid operated injectioncontrol valve, said injection control valve housing mounted in abutmentwith said distributor housing to form a cavity for receiving saidreverse flow restrictor valve.
 152. A high pressure fuel system forsupplying fuel at a predetermined pressure through plural fuel injectionlines to the corresponding cylinders of a multi-cylinder internalcombustion engine, comprising:a fuel supply means for supplying fuel fordelivery to the internal combustion engine, said fuel supply meansincluding a fuel transfer circuit; a drain passage for connection tosaid fuel transfer circuit; a high pressure pump means for pressurizingfuel above the predetermined pressure; a fuel distributor meansfluidically connected with said high pressure pump means through saidfuel transfer circuit for enabling sequential periodic fluidiccommunication with the engine cylinders through the corresponding fuelinjection lines; an injection control valve positioned within said fueltransfer circuit between said high pressure pump means and said fueldistributor means for controlling the fuel injected into each enginecylinder during each of the sequential periods of communication enabledby said fuel distributor means to thereby define sequential injectionevents, said injection control valve is movable between an open positionallowing fuel flow from said high pressure pump means to said fueldistributor means and a closed position blocking flow from said highpressure pump means while fluidically connecting said drain passage tosaid fuel transfer circuit downstream of said injection control valve; acavitation control means for minimizing cavitation in said fuel transfercircuit and the fuel injection lines between said injection controlvalve and the engine cylinders, said cavitation control means operableto maintain fuel in said fuel transfer circuit downstream of said fueldistributor means, said cavitation control means including an auxiliaryfuel supply connected to said drain passage for supplying pressurizedfuel at an auxiliary supply pressure to said fuel transfer circuitdownstream of said injection control valve when said injection controlvalve is in said closed position, wherein said auxiliary supply pressureis high enough to minimize the effects of cavitation while low enough tocause no fuel injection.
 153. The high pressure fuel system of claim152, further including an accumulator means positioned along said fueltransfer circuit between said high pressure pump means and saidinjection control valve for accumulating and temporarily storing fuel athigh pressure received from said high pressure pump means.
 154. The highpressure fuel system of claim 149, wherein said fuel distributor meansincludes a distributor housing containing a rotor bore and a distributorrotor mounted for rotation in said rotor bore, said cavitation controlmeans including a refill means for refilling the plural injection lines,said refill means including a boost pump means for supplying fuel at aboost pressure to said pump means, a boost pump outlet passagefluidically connecting said boost pump means to said pump means, and arefill port formed in said distributor rotor and continuouslyfluidically connected to said boost pump outlet passage, rotation ofsaid distributor rotor causing said refill port to periodicallyfluidically connect said boost pump outlet passage to each of the pluralinjection lines so as to maintain fuel in the plural injection lines atboost pressure.
 155. A high pressure fuel system for supplying fuel at apredetermined pressure through plural fuel injection lines to thecorresponding cylinders of a multi-cylinder internal combustion engine,comprising:a fuel supply means for supplying fuel for delivery to theinternal combustion engine, said fuel supply means including a fueltransfer circuit; a drain passage for connection to said fuel transfercircuit; a high pressure pump means for pressurizing fuel above thepredetermined pressure; a fuel distributor means fluidically connectedwith said high pressure pump means through said fuel transfer circuitfor enabling sequential periodic fluidic communication with the enginecylinders through the corresponding fuel injection lines; an injectioncontrol valve positioned within said fuel transfer circuit between saidhigh pressure pump means and said fuel distributor means for controllingthe fuel injected into each engine cylinder during each of thesequential periods of communication enabled by said fuel distributormeans, wherein said injection control valve is movable between an openposition allowing fuel flow to said fuel distributor means and a closedposition blocking flow from said accumulator means while fluidicallyconnecting said drain passage to said fuel transfer circuit downstreamof said injection control valve, wherein movement of said injectioncontrol valve from said open position to said closed position and fromsaid closed position to said open position defines a draining event andmovement of said injection control valve from said closed position tosaid open position and from said open position to said closed positiondefines an injection event; a cavitation control means for minimizingcavitation in said fuel transfer circuit and the fuel injection linesbetween said injection control valve and the engine cylinders, saidcavitation control means including a pressure regulating meanspositioned in said drain passage for maintaining fuel in said fueltransfer circuit downstream of said injection control valve and in thefuel injection lines at a regulated pressure during said draining event.156. The high pressure fuel system of claim 155, further including anaccumulator means positioned along said fuel transfer circuit betweensaid high pressure pump means and said injection control valve foraccumulating and temporarily storing fuel at high pressure received fromsaid high pressure pump means.
 157. The high pressure fuel system ofclaim 156, further including a refill passage fluidically connected atone end to said drain passage between said injection control valve andsaid pressure regulating means and at an opposite end to said fueldistributor means, wherein said fuel distributor means further functionsto periodically fluidically connect said refill passage to the pluralinjection lines so as to maintain fuel in the plural injection lines atsaid regulated pressure.
 158. The high pressure fuel system of claim157, wherein said pressure regulating means includes a cylinderincluding a first end and a second end, a piston slidably mounted insaid cylinder and a biasing means for biasing said piston toward saidfirst end to force fuel into said refill passage.
 159. The high pressurefuel system of claim 158, wherein said biasing means includes a coilspring positioned in abutment with said piston adjacent said second endof said cylinder.
 160. The high pressure fuel system of claim 158,wherein said biasing means includes a supply of pressurized biasingfluid.
 161. The high pressure fuel system of claim 160, wherein saidsupply of pressurized biasing fluid is accumulator fuel.
 162. The highpressure fuel pump assembly of claim 1, wherein said fuel distributormeans includes a plurality of injection line valves for controlling theflow of fuel to corresponding cylinders through corresponding fuelinjection lines, each of said injection line valves including a slidevalve element reciprocally mounted in said distributor housing.
 163. Thehigh pressure fuel pump assembly of claim 162, wherein said fueldistributor means further includes a distributor camshaft rotationallymounted in said distributor housing, said distributor camshaft includingat least one cam for causing said distributor slide valve elements toreciprocate as said distributor camshaft is rotated, wherein said slidevalves are mounted for reciprocal movement along axial lines,respectively, that are parallel to the rotational axis of saiddistributor camshaft.
 164. The high pressure fuel pump assembly of claim163, wherein each of said plurality of slide valve elements is movableinto an open position to define a respective fuel injection periodduring which high pressure fuel may flow to the respective enginecylinder via the respective fuel injection line and a closed positionblocking fuel flow through said respective fuel injection line, each ofsaid plurality of injection line valves being of the spool-typeincluding a land formed on said slide valve element for blocking fuelflow when said respective injection line valve is in said closedposition.
 165. The high pressure fuel pump assembly of claim 164,wherein said slide valve element includes a cylindrical portion having afirst end and a second end, an annular groove formed in said cylindricalportion adjacent said land for permitting fuel to flow to the enginecylinders when said respective injection line valve is in said openposition, further including a biasing means positioned adjacent saidfirst end for biasing said second end into abutment with said at leastone cam.
 166. The high pressure fuel pump assembly of claim 11, furtherincluding a distributor housing mounted on said pump housing, said fueldistributor means including a plurality of injection line valves forcontrolling the flow of fuel to corresponding cylinders throughcorresponding fuel injection lines, each of said injection line valvesincluding a slide valve element reciprocally mounted in said distributorhousing.
 167. The high pressure fuel pump assembly of claim 166, whereinsaid fuel distributor means further includes a distributor camshaftrotationally mounted in said distributor housing, said distributorcamshaft including at least one cam for causing said distributor slidevalve elements to reciprocate as said distributor camshaft is rotated.168. The high pressure fuel pump assembly of claim 167, wherein each ofsaid plurality of slide valve elements is movable into an open positionto define a respective fuel injection period during which high pressurefuel may flow to the respective engine cylinder via the respective fuelinjection line and a closed position blocking fuel flow through saidrespective fuel injection line, each of said plurality of injection linevalves being of the spool-type including a land formed on said slidevalve element for blocking fuel flow when said respective injection linevalve is in said closed position.
 169. The high pressure fuel pumpassembly of claim 168, wherein said slide valve element includes acylindrical portion having a first end and a second end, an annulargroove formed in said cylindrical portion adjacent said land forpermitting fuel to flow to the engine cylinders when said respectiveinjection line valve is in said open position, further including abiasing means positioned adjacent said first end for biasing said secondend into abutment with said at least one cam.
 170. The fuel pumpassembly of claim 82, wherein said pump head forms at least a partialend wall for said pump chamber, said pump chamber being positionedimmediately adjacent said pump head.
 171. The fuel pump assembly ofclaim 82, wherein said pump barrel is a one piece structure including aninner end positioned in abutment with said pump head.
 172. The fuel pumpassembly of claim 171, wherein said pump barrel includes a pump inletpassage adapted to communicate with a source of fuel for feeding fuelinto said pump chamber and a pump outlet passage through which fuel maybe discharged from said pump chamber and wherein said pump unit includesa pump unit check valve mounted at least partially within said pumpoutlet passage for permitting only one way flow of fuel from said pumpchamber through said pump outlet passage, said pump unit check valveincluding a check valve seat formed on said pump barrel.
 173. The fuelpump assembly of claim 170, wherein said pump head includes a pump inletpassage adapted to communicate with a source of fuel for feeding fuelinto said pump chamber and a pump outlet passage through which fuel maybe discharged from said pump chamber and further including a pump unitcheck valve mounted within said pump outlet passage for permitting onlyone way flow of fuel from said pump chamber through said pump unitoutlet passage, said pump unit check valve including a check valve seatformed on said pump head.
 174. The fuel pump assembly of claim 82,wherein said pump head includes a delivery passage for receiving highpressure fuel from said pumping chamber, said pump barrel including aninner end positioned in abutment with said pump head to form a highpressure joint exposed to high pressure fuel delivered from said pumpchamber to said delivery passage, said high pressure joint being theonly joint positioned between said pumping chamber and said deliverypassage exposed to high pressure fuel.
 175. The fuel pump assembly ofclaim 83, further including a plurality of pump unit control valvesassociated with said pump chambers, respectively, for controlling theamount of high pressure fuel pumped out of the corresponding pumpchamber by a corresponding pump plunger, and a valve cavity formed ineach of said pump barrels, each of said plurality of pump unit controlvalves including a control valve element mounted for reciprocal movementin a respective valve cavity.
 176. The fuel pump assembly of claim 175,wherein each of said plurality of pump unit control valves includes anannular valve seat formed on the corresponding pump barrel in said valvecavity.
 177. The fuel pump assembly of claim 176, wherein each said pumpchamber extends through the corresponding pump barrel along a radialpump axis and opens into the corresponding valve cavity, said valvecavity extending diametrically through said pump barrel substantiallyperpendicular to said radial pump axis.
 178. The fuel pump assembly ofclaim 177, wherein each said replaceable pump unit includes a pump unitinlet communicating with a source of fuel for feeding fuel into saidpump chamber and a pump unit outlet, wherein said pump unit includes apump unit check valve for permitting only one way flow of fuel from thepump chamber through said pump unit outlet, said control valve elementpositioned along said radial pump axis between said pump chamber andsaid pump unit check valve.
 179. The fuel pump assembly of claim 178,wherein said control valve element is movable between an open positionpermitting fuel flow from the corresponding pump chamber and a closedposition blocking fuel flow from said pump chamber through said pumpunit outlet, said control valve element being pressure balanced in theclosed position.
 180. The fuel pump assembly of claim 82, furtherincluding an accumulator means containing at least one accumulatorchamber for accumulating and temporarily storing fuel at high pressurereceived from said pump chamber, wherein said accumulator means includesan accumulator housing and at least one accumulator chamber formed insaid accumulator housing, said accumulator housing being positioned aspaced distance from said pump head.
 181. A fuel pump assembly,comprisinga pump housing containing an outwardly opening pump cavity, apump head mountable on the pump housing to close the outwardly openingpump cavity, said pump head containing a pump unit recess positioned tocommunicate with the pump cavity, a pump unit mounted within said pumpunit recess, said pump unit including a pump barrel containing a pumpchamber and a pump plunger adapted to be mounted for reciprocal movementwithin said pump chamber, said pump barrel containing a valve cavity,and a variable displacement pump control valve means mounted in saidvalve cavity for varying the effective displacement of said pump unit inresponse to a variable displacement control signal.
 182. The fuel pumpassembly of claim 181, wherein said pump housing includes a plurality ofsaid outwardly opening pump cavities, said pump head containing aplurality of said pump unit recesses positioned to communicate with saidpump cavities, respectively, and further including a plurality of saidpump units, each said pump unit including a pump barrel containing apump chamber, a pump plunger mounted for reciprocation within said pumpchamber when said drive shaft rotates and a retaining means for mountingsaid pump unit within a corresponding said pump unit recess of said pumphead in a position to extend at least partially into said pump cavity inspaced apart non-contacting relationship with said pump housing. 183.The fuel pump assembly of claim 182, wherein said drive shaft includes aplurality of cams for causing said pump plungers to reciprocate, andfurther including a plurality of tappet assemblies associated with saidpump units, respectively, each said tappet assembly being mounted forreciprocal movement within a corresponding pump cavity and beingconnected with a corresponding pump plunger, and a plurality of tappetbias springs for biasing said tappet assemblies into engagement withsaid cams, respectively, to cause said tappet assemblies and theconnected pump plungers to reciprocate as said drive shaft is rotated.184. The fuel pump assembly of claim 183, wherein said pump housing isan integral single piece structure including a head engaging surface forprecisely positioning said pump head and tappet guiding surfaces withinsaid pump cavities for guiding said tappets, respectively, said pumphousing further including a radially enclosed drive shaft cavity havingsubstantial radial openings only through said pump cavities, said pumphousing including drive shaft support surfaces for precisely supportingsaid drive shaft, said pump housing requiring close tolerance machiningof only said head engaging surface, said tappet guiding surfaces andsaid drive shaft support surfaces to provide suitable alignment of saidpump chambers with respect to said tappets and said drive shaft.
 185. Afuel pump assembly, comprisinga pump housing containing an outwardlyopening pump cavity, a pump head mountable on the pump housing to closethe outwardly opening pump cavity, said pump head containing a pump unitrecess positioned to communicate with the pump cavity and a valve cavityhaving a central axis aligned with a central axis of said pump unitrecess, a pump unit mounted within said pump unit recess, said pump unitincluding a pump barrel containing a pump chamber and a pump plungeradapted to be mounted for reciprocal movement within said pump chamber,and a variable displacement control valve means mounted in said valvecavity for varying the effective displacement of said pump unit inresponse to a variable displacement control signal.
 186. The fuel pumpassembly of claim 83, further including a plurality of pump unit controlvalves associated with said pump chambers, respectively, for controllingthe effective displacement of each said associated pump plunger, saidpump head including a first side for engaging said pump housing and asecond side formed opposite said first side, said plurality of pump unitcontrol valves mounted on said second side of said pump head directlyopposite corresponding pump unit recesses.
 187. A fuel pump assembly forsupplying fuel to a multi-cylinder engine above a predetermined highpressure, comprising:a pump housing containing an outwardly opening pumpcavity, a drive shaft rotatably mounted in the pump housing, a singlepiece, integral pump head mountable on said pump housing to close saidoutwardly opening pump cavity, said integral pump head containing a pumpchamber and at least one accumulator chamber for temporarily storingfuel under pressure received from said pump chamber; a pump plungeradapted to be mounted for reciprocal movement within said pump chamberin response to rotation of said drive shaft; and distributor means forsequentially distributing fuel to said engine cylinders from said atleast one accumulator chamber.
 188. The fuel pump assembly of claim 187,wherein said pump head includes an integral pump barrel surrounding saidpump chamber and extending into said outwardly opening pump cavity. 189.The fuel pump assembly of claim 188, wherein said pump housing includesa plurality of said outwardly opening pump cavities, said pump headcontaining a plurality of said integrally formed pump barrels, each ofsaid integrally formed pump barrels containing a pump chamber, andfurther including a plurality of pump plungers mounted for reciprocationwithin said pump chambers, respectively, when said drive shaft rotates.190. The fuel pump assembly of claim 189, wherein said drive shaftincludes a plurality of cams for causing said pump plungers toreciprocate.
 191. The fuel pump assembly of claim 190, further includinga plurality of tappet assemblies associated with said pump units,respectively, each said tappet assembly being mounted for reciprocalmovement within a corresponding pump cavity and being connected with acorresponding pump plunger, and a plurality of tappet bias springs forbiasing said tappet assemblies into engagement with said cams,respectively, to cause said tappet assemblies and the connected pumpplungers to reciprocate as said drive shaft is rotated.
 192. The fuelpump assembly of claim 191, wherein said pump head includes a pluralityof annular spring recesses formed around said integrally formed pumpbarrels for receiving a corresponding tappet bias spring.